Showing posts with label EIGRP. Show all posts
Showing posts with label EIGRP. Show all posts

Thursday, 15 January 2026

IPv6 Redistribution between EIGRPv3, OSPFv3 and RIPng

 **IPv6 Route Redistribution** 

Route redistribution in IPv6 allows different routing protocols (e.g., OSPFv3, EIGRP for IPv6, BGP, RIPng, IS-IS) to exchange routing information within the same network. This is useful in multi-vendor or multiprotocol environments where migration or integration is required.

 


**Key Points:**

- Redistribution is typically configured on routers that run multiple routing protocols.

- Careful planning is needed to avoid routing loops, suboptimal paths, or convergence issues.

- Use route filtering, metrics, and administrative distance tuning to control redistribution.

- Default metrics often need manual assignment when redistributing between protocols (e.g., OSPF to EIGRP).

 

**Example Use Case:** 

Connecting an OSPFv3 domain with a BGP IPv6 network, allowing internal routes to be advertised externally and vice versa.

 

**Configuration Note:** 

Always verify routes after redistribution and ensure prefix lengths and next-hop addresses are correctly advertised.


Let's see the configuration:-


Task:

  • Configure the topology as per the diagram
  • Configure the IPv6 addresses as per the topology
  • Configure EIGRPv3 on router 1 and advertise directly 
  • Configure OSPFv3 on router 2 and advertise FastEthernet 2/0 - 3/0
  • Configure EIGRPv3 on router 2 and advertise FastEthernet 0/0
  • Configure OSPFv3 on router 3 and advertise FastEthernet 3/0
  • Configure RIPng on router 3 and advertise FastEthernet 2/0
  • Configure redistribution between EIGRPv3 and OSPFv3 and vice versa 
  • Configure redistribution between RIPng and OSPFv3 and vice versa
  • Make sure all the routes are exchanged 
  • ensure the connectivity and verify with show commands



R1(config)#ipv6 unicast-routing
R1(config)#interface fastethernet 0/0
R1(config-if)#ipv6 address 2001:1122:1122:1122::1/64
R1(config-if)#no shutdown
R1(config-if)#exit

R1(config)#interface fastethernet 2/0
R1(config-if)#ipv6 address fc00:1111:1111:1111::1/64
R1(config-if)#no shutdown
R1(config-if)#no keepalive
R1(config-if)#exit
R1(config)#

R2(config)#ipv6 unicast-routing
R2(config)#interface fastethernet 0/0
R2(config-if)#ipv6 address 2001:1122:1122:1122::2/64
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface fastethernet 2/0
R2(config-if)#ipv6 address fc00:2222:2222:2222::1/64
R2(config-if)#no shutdown
R2(config-if)#no keepalive
R2(config-if)#exit
R2(config)#interface fastethernet 3/0
R2(config-if)#ipv6 address 2001:2233:2233:2233::1/64
R2(config-if)#no shutdown
R2(config-if)#exit



R3#show ipv6 interface brief
FastEthernet0/0            [administratively down/down]
    unassigned
ATM1/0                     [administratively down/down]
    unassigned
FastEthernet2/0            [up/up]
    FE80::C803:A5FF:FE68:38
    FC00:3333:3333:3333::1
FastEthernet3/0            [up/up]
    FE80::C803:A5FF:FE68:54
    2001:2233:2233:2233::2


R1(config)#ipv6 router eigrp 65100
R1(config-rtr)#no shutdown
R1(config-rtr)#router-id 11.11.11.11
R1(config-rtr)#exit

R1(config)#interface fastethernet 0/0
R1(config-if)#ipv6 eigrp 65100
R1(config-if)#exit

R1(config)#interface fastethernet 2/0
R1(config-if)#ipv6 eigrp 65100
R1(config-if)#exit

R2(config)#ipv6 router eigrp 65100
R2(config-rtr)#no shutdown
R2(config-rtr)#router-id 22.22.22.22
R2(config-rtr)#exit

R2(config)#interface fastethernet 0/0
R2(config-if)#ipv6 eigrp 65100
R2(config-if)#exit

R2(config)#IPv6 router ospf 100
R2(config-rtr)#router-id 22.22.22.22
R2(config-rtr)#exit

R2(config)#interface fastethernet 2/0
R2(config-if)#ipv6 ospf 100 area 0
R2(config-if)#exit

R2(config)#interface fastethernet 3/0
R2(config-if)#ipv6 ospf 100 area 0
R2(config-if)#exit


R3(config)#IPv6 router ospf 100
R3(config-rtr)#router-id 33.33.33.33
R3(config-rtr)#exit

R3(config)#interface fastethernet 3/0
R3(config-if)#ipv6 ospf 100 area 0
R3(config-if)#exit


R3(config)#ipv6 unicast-routing
R3(config)#interface fastEthernet 2/0
R3(config-if)#ipv6 rip internetworks enable
R3(config-if)#exit


R2(config)#ipv6 router ospf 100
R2(config-rtr)#redistribute eigrp 65100 metric 100 metric-type 1 include-connected
R2(config-rtr)#exit

R2(config)#ipv6 router eigrp 65100
R2(config-rtr)#redistribute ospf 100 include-connected metric 1000 2000 255 1 1500
 metric <bw> <delay> <reliability> <load> <mtu>
R2(config-rtr)#exit

R3(config)#ipv6 router ospf 100
R3(config-rtr)#redistribute rip internetworks include-connected metric 100 metric-type 1
R3(config-rtr)#exit


R1#show ipv6 route
IPv6 Routing Table - Default - 8 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, M - MIPv6, R - RIP, I1 - ISIS L1
       I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary, D - EIGRP
       EX - EIGRP external
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
C   2001:1122:1122:1122::/64 [0/0]
     via FastEthernet0/0, directly connected
L   2001:1122:1122:1122::1/128 [0/0]
     via FastEthernet0/0, receive
EX  2001:2233:2233:2233::/64 [170/3074560]
     via FE80::C802:59FF:FE98:0, FastEthernet0/0
C   FC00:1111:1111:1111::/64 [0/0]
     via FastEthernet2/0, directly connected
L   FC00:1111:1111:1111::1/128 [0/0]
     via FastEthernet2/0, receive
EX  FC00:2222:2222:2222::/64 [170/3074560]
     via FE80::C802:59FF:FE98:0, FastEthernet0/0
EX  FC00:3333:3333:3333::/64 [170/3074560]
     via FE80::C802:59FF:FE98:0, FastEthernet0/0
L   FF00::/8 [0/0]
     via Null0, receive

R2#show ipv6 protocol
IPv6 Routing Protocol is "connected"
IPv6 Routing Protocol is "eigrp 65100"
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  EIGRP maximum hopcount 100
  EIGRP maximum metric variance 1
  Interfaces:
    FastEthernet0/0
  Redistribution:
    Redistributing protocol ospf 100 with metric 0 include-connected
  Maximum path: 16
  Distance: internal 90 external 170

IPv6 Routing Protocol is "ospf 100"
  Interfaces (Area 0):
    FastEthernet3/0
    FastEthernet2/0
  Redistribution:
    Redistributing protocol eigrp 65100 with metric 100 type 1 include-connected

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Monday, 12 January 2026

IPv6 EIGRP: The Next-Generation Routing Protocol

 IPv6 EIGRP: The Next-Generation Routing Protocol

As networks transition to IPv6, routing protocols must evolve too. Enter EIGRP for IPv6 – Cisco’s enhanced interior gateway protocol, now ready for the modern internet.

 

What is IPv6 EIGRP?

IPv6 EIGRP is the IPv6-enabled version of Cisco’s advanced distance-vector protocol. It retains EIGRP’s popular features – rapid convergence, low bandwidth usage, and support for VLSM – while fully embracing IPv6 addressing and communication.




 

Key Advantages

Dual-Stack Ready: Runs alongside IPv4 EIGRP, allowing gradual migration

Separate Process: IPv6 EIGRP operates as an independent protocol instance

Link-local addressing: uses IPv6 link-local addresses for neighbor discovery

Same Dual Algorithm: Maintains the reliable loop-free path selection

 

Configuration Highlights

 

R1(config)#ipv6 unicast-routing
R1(config)#ipv6 router eigrp 65100
R1(config-rtr)#no shutdown
R1(config-rtr)#router-id 11.11.11.11
R1(config-rtr)#exit
R1(config)#interface fastethernet 0/0
R1(config-if)#ipv6 eigrp 65100
R1(config-if)#exit  

Let's see the configuration :

Topology:










TASK
  • Configure the topology as per the diagram 
  • Configure IPv6 addresses as per the topology
  • Configure IPv6 EIGRP AS 65100
  • Make sure both routers communicate 
  • Verify with show commands 
R1(config)#ipv6 unicast-routing
R1(config)#
R1(config)#interface fastethernet 0/0
R1(config-if)#ipv6 address 2001:1122:1122:1122::1/64
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#
R1(config)#
R1(config)#interface fastethernet 2/0
R1(config-if)#ipv6 address fc00:1111:1111:1111::1/64
R1(config-if)#no shutdown
R1(config-if)#no keepalive
R1(config-if)#exit


R2(config)#ipv6 unicast-routing
R2(config)#
R2(config)#interface fastethernet 0/0
R2(config-if)#ipv6 address 2001:1122:1122:1122::2/64
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#
R2(config)#interface fastethernet 2/0
R2(config-if)#ipv6 address fc00:2222:2222:2222::1/64
R2(config-if)#no shutdown
R2(config-if)#no keepalive
R2(config-if)#exit


R1(config)#ipv6 router eigrp 65100
R1(config-rtr)#no shutdown
R1(config-rtr)#router-id 11.11.11.11
R1(config-rtr)#exit
R1(config)#
R1(config)#interface fastethernet 0/0
R1(config-if)#ipv6 eigrp 65100
R1(config-if)#exit
R1(config)#
R1(config)#interface fastethernet 2/0
R1(config-if)#ipv6 eigrp 65100
R1(config-if)#exit


R2(config)#ipv6 router eigrp 65100
R2(config-rtr)#no shutdown
R2(config-rtr)#router-id 22.22.22.22
R2(config-rtr)#exit
R2(config)#
R2(config)#interface fastethernet 0/0
R2(config-if)#ipv6 eigrp 65100
R2(config-if)#exit
R2(config)#
R2(config)#interface fastethernet 2/0
R2(config-if)#ipv6 eigrp 65100
R2(config-if)#exit


R1#show ipv6 route
IPv6 Routing Table - Default - 6 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, M - MIPv6, R - RIP, I1 - ISIS L1
       I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary, D - EIGRP
       EX - EIGRP external
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
C   2001:1122:1122:1122::/64 [0/0]
     via FastEthernet0/0, directly connected
L   2001:1122:1122:1122::1/128 [0/0]
     via FastEthernet0/0, receive
C   FC00:1111:1111:1111::/64 [0/0]
     via FastEthernet2/0, directly connected
L   FC00:1111:1111:1111::1/128 [0/0]
     via FastEthernet2/0, receive
D   FC00:2222:2222:2222::/64 [90/30720]
     via FE80::C802:59FF:FE98:0, FastEthernet0/0
L   FF00::/8 [0/0]
     via Null0, receive

R1#show ipv6 eigrp neighbor
IPv6-EIGRP neighbors for process 65100
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   Link-local address:     Fa0/0             12 00:01:21  906  5000  0  5
    FE80::C802:59FF:FE98:0

R1#show ipv6 interface brief
FastEthernet0/0            [up/up]
    FE80::C801:A5FF:FED4:0
    2001:1122:1122:1122::1
ATM1/0                     [administratively down/down]
    unassigned
FastEthernet2/0            [up/up]
    FE80::C801:A5FF:FED4:38
    FC00:1111:1111:1111::1

R1#ping fc00:2222:2222:2222::1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FC00:2222:2222:2222::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/29/56 ms



















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Saturday, 30 August 2025

What is an Offset-list? How to configure EIGRP Offset-list?

 What is an Offset-list?

An Offset-list is an EIGRP and RIPv2 feature that allows you to add a fixed value (an “offset”) to the composite metric of a route that matches an access control list (ACL). You can apply this to inbound (IN) and outbound (OUT) routing updates.

By increasing the metric of a route, you make it less preferable. EIGRP will always choose the path with the lower composite metric. It’s a simple yet powerful way to de-prioritize a path without using a route filter to deny it entirely. Offset value to add to the matric (1-2147483647)





Why would you use one?

Common use cases include:

  • ·        Basic load balance: making a primary link preferred while keeping a backup link active by making its metric slightly worse.
  • ·        Policy-based routing: influencing outbound traffic to take a specific path based on network policy.
  • ·        Cost engineering: simulating a longer path for a route learned from one neighbor compared to another.

 let's see the configuration:-

Topology:-



  • Configure the topology as per the diagram
  • Configure the IP addresses as per the topology 
  • Configure EIGRP 100 to advertise directly connected interfaces
  • Configure access-list standard permit 30.1.1.1 network
  • Make sure router 1 will use the serial 5/0 to reach the 30.1.1.1/8 network
  • Ensure no load balancing is used with the offset list; add 5000 metrics to the serial 5/3 route.

R1(config)#interface serial 5/0
R1(config-if)#ip address 1.1.1.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial 5/3
R1(config-if)#ip address 4.4.4.2 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface FastEthernet 0/0
R1(config-if)#ip address 10.1.1.1 255.0.0.0
R1(config-if)#no keepalive
R1(config-if)#no shutdown
R1(config-if)#exit

R2(config)#interface serial 5/0
R2(config-if)#ip address 1.1.1.2 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 5/1
R2(config-if)#ip address 2.2.2.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface FastEthernet 0/0
R2(config-if)#ip address 20.1.1.1 255.0.0.0
R2(config-if)#no keepalive
R2(config-if)#no shutdown
R2(config-if)#exit

R3(config)#interface serial 5/2
R3(config-if)#ip address 3.3.3.1 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface serial 5/1
R3(config-if)#ip address 2.2.2.2 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface FastEthernet 0/0
R3(config-if)#ip address 30.1.1.1 255.0.0.0
R3(config-if)#no keepalive
R3(config-if)#no shutdown
R3(config-if)#exit

R4(config)#interface serial 5/2
R4(config-if)#ip address 3.3.3.2 255.0.0.0
R4(config-if)#no shutdown
R4(config-if)#exit
R4(config)#interface serial 5/3
R4(config-if)#ip address 4.4.4.1 255.0.0.0
R4(config-if)#no shutdown
R4(config-if)#exit
R4(config)#interface FastEthernet 0/0
R4(config-if)#ip address 40.1.1.1 255.0.0.0
R4(config-if)#no keepalive
R4(config-if)#no shutdown
R4(config-if)#exit

R1(config)#router eigrp 100
R1(config-router)#network 10.0.0.0
R1(config-router)#network 1.0.0.0
R1(config-router)#network 4.0.0.0
R1(config-router)#no auto-summary
R1(config-router)#exit


R2(config)#router eigrp 100
R2(config-router)#network 20.0.0.0
R2(config-router)#network 1.0.0.0
R2(config-router)#network 2.0.0.0
R2(config-router)#no auto-summary
R2(config-router)#exit


R3(config)#router eigrp 100
R3(config-router)#network 30.0.0.0
R3(config-router)#network 3.0.0.0
R3(config-router)#network 2.0.0.0
R3(config-router)#no auto-summary
R3(config-router)#exit

R4(config)#router eigrp 100
R4(config-router)#network 40.0.0.0
R4(config-router)#network 3.0.0.0
R4(config-router)#network 4.0.0.0
R4(config-router)#no auto-summary
R4(config-router)#exit

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

C    1.0.0.0/8 is directly connected, Serial5/0
D    2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:26:52, Serial5/0
D    3.0.0.0/8 [90/2681856] via 4.4.4.1, 00:26:52, Serial5/3
C    4.0.0.0/8 is directly connected, Serial5/3
D    20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:26:52, Serial5/0
D    40.0.0.0/8 [90/2172416] via 4.4.4.1, 00:26:52, Serial5/3
C    10.0.0.0/8 is directly connected, FastEthernet0/0
D    30.0.0.0/8 [90/2684416] via 4.4.4.1, 00:24:15, Serial5/3
                [90/2684416] via 1.1.1.2, 00:24:15, Serial5/0

R1#traceroute 30.1.1.1

Type escape sequence to abort.
Tracing the route to 30.1.1.1

  1 4.4.4.1 48 msec
    1.1.1.2 28 msec
    4.4.4.1 28 msec
  2 2.2.2.2 80 msec
    3.3.3.1 80 msec
    2.2.2.2 80 msec
R1#show ip route 30.1.1.1 255.0.0.0
Routing entry for 30.0.0.0/8
  Known via "eigrp 100", distance 90, metric 2684416, type internal
  Redistributing via eigrp 100
  Last update from 4.4.4.1 on Serial5/3, 00:01:28 ago
  Routing Descriptor Blocks:
    4.4.4.1, from 4.4.4.1, 00:01:28 ago, via Serial5/3
      Route metric is 2684416, traffic share count is 1
      Total delay is 40100 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2
  * 1.1.1.2, from 1.1.1.2, 00:01:28 ago, via Serial5/0
      Route metric is 2684416, traffic share count is 1
      Total delay is 40100 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2

(as you can see, both route metrics are the same. So now we are going to add 5000 metric to the serial 5/3 route.


R1(config)#ip access-list standard Offset
R1(config-std-nacl)#permit 30.0.0.0 0.255.255.255
R1(config-std-nacl)#exit

R1(config)#router eigrp 100
R1(config-router)#offset-list Offset in  5000 serial 5/3
R1(config-router)#end

*Aug 30 16:14:11.471: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 4.4.4.1 (Serial5/3) is resync: route configuration changed

R1#clear ip route *

R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

C    1.0.0.0/8 is directly connected, Serial5/0
D    2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:00:39, Serial5/0
D    3.0.0.0/8 [90/2681856] via 4.4.4.1, 00:00:39, Serial5/3
C    4.0.0.0/8 is directly connected, Serial5/3
D    20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:00:39, Serial5/0
D    40.0.0.0/8 [90/2172416] via 4.4.4.1, 00:00:39, Serial5/3
C    10.0.0.0/8 is directly connected, FastEthernet0/0
D    30.0.0.0/8 [90/2684416] via 1.1.1.2, 00:00:39, Serial5/0


R1#traceroute 30.1.1.1

Type escape sequence to abort.
Tracing the route to 30.1.1.1

  1 1.1.1.2 40 msec 32 msec 32 msec
  2 2.2.2.2 76 msec 56 msec 72 msec


R1#show ip route 30.1.1.1 255.0.0.0
Routing entry for 30.0.0.0/8
  Known via "eigrp 100", distance 90, metric 2684416, type internal
  Redistributing via eigrp 100
  Last update from 1.1.1.2 on Serial5/0, 00:01:57 ago
  Routing Descriptor Blocks:
  * 1.1.1.2, from 1.1.1.2, 00:01:57 ago, via Serial5/0
      Route metric is 2684416, traffic share count is 1
      Total delay is 40100 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2

R1#show ip eigrp topology
IP-EIGRP Topology Table for AS(100)/ID(10.1.1.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status
P 1.0.0.0/8, 1 successors, FD is 2169856
        via Connected, Serial5/0
P 2.0.0.0/8, 1 successors, FD is 2681856
        via 1.1.1.2 (2681856/2169856), Serial5/0
P 3.0.0.0/8, 1 successors, FD is 2681856
        via 4.4.4.1 (2681856/2169856), Serial5/3
P 4.0.0.0/8, 1 successors, FD is 2169856
        via Connected, Serial5/3
P 10.0.0.0/8, 1 successors, FD is 28160
        via Connected, FastEthernet0/0
P 20.0.0.0/8, 1 successors, FD is 2172416
        via 1.1.1.2 (2172416/28160), Serial5/0
P 30.0.0.0/8, 1 successors, FD is 2684416
        via 1.1.1.2 (2684416/2172416), Serial5/0
        via 4.4.4.1 (2689416/2177416), Serial5/3
P 40.0.0.0/8, 1 successors, FD is 2172416
        via 4.4.4.1 (2172416/28160), Serial5/3

 ( as you can see, the metric has been increased to 2177416, and previously this metric was 2172416)

I hope you like this lab. Please visit our YouTube channel https://www.youtube.com/@internetworkss

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Tuesday, 6 November 2018

What is Stuck In Active (EIGRP)?




Stuck In Active (EIGRP)

The EIGRP convergence is the process when going active on a route is sometimes also by the name of the underlying algorithm, diffusing update algorithm (DUAL).




When a successor path is lost and there is no feasible successor is identified, the EIGRP router sends out queries on all interfaces in an attempt to identify an alternate path. EIGRP routers don’t select the successor until the EIGRP router receives a reply to all queries. When a router has received a reply for all its query messages, that router can safely use the best of the routes confirmed to be loop-free. The process can and does work well in many cases, often converging to a new route in less than 10 seconds.  If a reply is missing for 3 minutes, the router becomes stuck in active (SIA). In that case, it reset the neighbor's relationship with the neighbors that did not reply to queries.

EIGRP sends every query and reply message using RTP, so every message is acknowledged using the EIGRP ACK message.
To limit the scope of queries, there are two tools: stub routers and route summarization this us to reduce the work performed by the DUAL and the scope of query messages.

EIGRP STUB

Stub routing is one way to limit queries. A stub router is one that is connected to more than two neighbors and should be a transit router. The EIGRP stub routing feature improves network stability, reduces resource utilization, and simplifies remote router (spoke) configuration. Stub routing is commonly used in a Hub-and-Spoke topology.

Here is the command:
R1(config-router)#EIGRP STUB?
  connected       Do advertise connected routes
  leak-map        Allow dynamic prefixes based on the leak-map
  receive-only    Set receive only neighbor
  redistributed   Do advertise redistributed routes
  static                 Do advertise static routes
  summary         Do advertise summary routes

·         Connected means the router advertises connected routes only for those interfaces that match with a network command.

·         Leak-map means the router advertises only which is specified by a leak-map

·         Receive-only means the router does not advertise any routes. This option can be used with any other option.

·         Redistribution means the router advertises only the redistributed routes.

·         Static means the router advertises only the static routes with redistributed static commands configured.

·         Summary means the router advertises only auto-summarized or statically configured summary routes



NOTE: By default, is connected and summary.

Before we start EIGRP configuration check out some important of EIGRP CCIE exam topics.

 Here are the lists of all EIGRP labs and theories CCNA to CCIE

 1.Enhanced Interior Gateway Routing Protocol (EIGRP)

2.Stuck In Active (EIGRP)

3.EIGRP Equal-Cost and Unequal-Cost load balancing

4.Route filtering passive interface

5.Route summarization

6.EIGRP STUB and Configuration

7.Routing Protocol Authentication (EIGRP ) and configuration





 


 


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What is EIGRP Equal-Cost and Unequal-Cost load balancing? What is variance? How to configure?




EIGRP Equal-Cost and Unequal-Cost load balancing

Routes with the lowest metric get installed in the routing table by default, if two or more routes have the same metric the router will install both the routes in the routing table this is called equal cost load balancing.

EIGRP does equal cost load balancing automatically, whereas unequal cost load balancing is not automatic, for unequal cost load balancing we need to enable Variance. EIGRP can load balancing up to six paths, and the default is four paths. 




The maximum number of paths are based on Cisco IOS versions and router platform. For the older Cisco IOS versions, the maximum-paths was 6. The latest version typically supports 16 or more.
 R1 (config)#router eigrp 100
R1 (config-router)#maximum-paths ?
  <1-32> Number of paths

Unequal cost load-balancing

EIGRP also supports unequal cost load balancing, it has to be done manually using variance. Variance is a multiplier value that ranges between ­(1 – 128) and the default is 1. The routes that can go for load balancing should satisfy the condition. The cost of the successor X variance > cost of the other routes to be used for load balancing
  • ·         The variance is multiplied by the current Feasible Distance.
  • ·         Any feasible successor whose calculated metric is less than or equal to the product of the variance and feasible distance is added to the IP routing table, assuming that the maximum-paths setting allows more routes
  • ·         Routes that are neither successor nor feasible successor routes can never add to the IP routing table, regardless of the variance setting. 
Before we start  EIGRP configuration check out some important of EIGRP CCIE exam topics.

 Here are the lists of all EIGRP labs and theories CCNA to CCIE

 1.Enhanced Interior Gateway Routing Protocol (EIGRP)

2.Stuck In Active (EIGRP)

3.EIGRP Equal-Cost and Unequal-Cost load balancing

4.Route filtering passive interface

5.Route summarization

6.EIGRP STUB and Configuration

7.Routing Protocol Authentication (EIGRP ) and configuration





Configuration of EIGRP Equal cost load balancing-

Topology:

  •      Configure the topology as per the diagram
  •          Advertise the interfaces using EIGRP 100
  •          Ensure the load balancing via traceroute.


R1#show ip interface  brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        10.1.1.1        YES manual up                    up
Serial3/0              1.1.1.1         YES manual up                    up
Serial3/3              4.4.4.2         YES manual up                    up

R2#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        20.1.1.1        YES manual up                    up
FastEthernet1/0        unassigned      YES unset  administratively down down
FastEthernet1/1        unassigned      YES unset  administratively down down
GigabitEthernet2/0     unassigned      YES unset  administratively down down
Serial3/0              1.1.1.2         YES manual up                    up
Serial3/1              2.2.2.1         YES manual up                    up

R3#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        30.1.1.1        YES manual up                    up
FastEthernet1/0        unassigned      YES unset  administratively down down
FastEthernet1/1        unassigned      YES unset  administratively down down
GigabitEthernet2/0     unassigned      YES unset  administratively down down
Serial3/0              unassigned      YES unset  administratively down down
Serial3/1              2.2.2.2         YES manual up                    up
Serial3/2              3.3.3.1         YES manual up                    up

R4#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        40.1.1.1        YES manual up                    up
Serial3/2              3.3.3.2         YES manual up                    up
Serial3/3              4.4.4.1         YES manual up                    up

R1(config)#router eigrp 100
R1(config-router)#network 1.0.0.0
R1(config-router)#network 4.0.0.0
R1(config-router)#network 10.0.0.0
R1(config-router)#no auto-summary

R2(config)#router eigrp 100
R2(config-router)#network 20.0.0.0
R2(config-router)#network 1.0.0.0
R2(config-router)#network 2.0.0.0
R2(config-router)#no auto-summary

R3(config)#router eigrp 100
R3(config-router)#network 30.0.0.0
R3(config-router)#network 2.0.0.0
R3(config-router)#network 3.0.0.0
R3(config-router)#no auto-summary


R4(config)#router eigrp 100
R4(config-router)#network 4.0.0.0
R4(config-router)#network 3.0.0.0
R4(config-router)#network 40.0.0.0
R4(config-router)#no auto-summary


R1#show ip eigrp 100 neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
1   4.4.4.1                 Se3/3                    12 00:15:50   37   222  0  8
0   1.1.1.2                 Se3/0                    13 00:17:52   67   402  0  20

R3#show  ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
1   3.3.3.2                 Se3/2                    12 00:17:17   41   246  0  9
0   2.2.2.1                 Se3/1                    11 00:17:45   48   288  0  19

R1#show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is not set

D     2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:17:19, Serial3/0
D     3.0.0.0/8 [90/2681856] via 4.4.4.1, 00:17:19, Serial3/3
D     20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:17:19, Serial3/0
D     30.0.0.0/8 [90/2684416] via 4.4.4.1, 00:17:19, Serial3/3
                 [90/2684416] via 1.1.1.2, 00:17:19, Serial3/0
D     40.0.0.0/8 [90/2172416] via 4.4.4.1, 00:17:19, Serial3/3




The above output you can see that the router R1 installed both routes in the routing table as it is using both the routes to reach the network 30.1.1.1.



R1#show  ip eigrp topology
EIGRP-IPv4 Topology Table for AS(100)/ID(10.1.1.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 2.0.0.0/8, 1 successors, FD is 2681856
        via 1.1.1.2 (2681856/2169856), Serial3/0
P 4.0.0.0/8, 1 successors, FD is 2169856
        via Connected, Serial3/3
P 10.0.0.0/8, 1 successors, FD is 28160
        via Connected, FastEthernet0/0
P 30.0.0.0/8, 2 successors, FD is 2684416
        via 1.1.1.2 (2684416/2172416), Serial3/0
        via 4.4.4.1 (2684416/2172416), Serial3/3
P 3.0.0.0/8, 1 successors, FD is 2681856
        via 4.4.4.1 (2681856/2169856), Serial3/3
P 40.0.0.0/8, 1 successors, FD is 2172416
        via 4.4.4.1 (2172416/28160), Serial3/3
P 1.0.0.0/8, 1 successors, FD is 2169856
        via Connected, Serial3/0
P 20.0.0.0/8, 1 successors, FD is 2172416
        via 1.1.1.2 (2172416/28160), Serial3/0

R1#traceroute 30.1.1.1
Type escape sequence to abort.
Tracing the route to 30.1.1.1
VRF info: (vrf in name/id, vrf out name/id)
  1 1.1.1.2 76 msec
    4.4.4.1 112 msec
    1.1.1.2 52 msec
  2 3.3.3.1 100 msec
    2.2.2.2 68 msec
    3.3.3.1 48 msec

now R1 is doing equal cost load balancing vea R2 and R4 because both the routes are having equal cost to reach network 30.1.1.1


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