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, EIGRP router sends out the 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 is 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 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 EIGRP ACK message.
To limit the scope of queries, there is two tools we use
stub routers and route summarization this us to reduce the work performed by
the DUAL and the scope of queries messages.
EIGRP STUB
Stub routing is one way to limit queries. A stub router is
one that is connected to on more than two neighbors and should be a transit
router. The EIGRP stub routing feature improve 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 advertise connected
routes only for those interfaces which matched with a network command.
·
Leak-map means the router advertise only which
is specified by a leak-map
·
Receive-only means the router do not advertise
any routes. And this option can be used with any other option.
·
Redistribution means the router advertise only
the redistributed routes.
·
Static means the router advertise only the
static routes with redistributed static command configured.
·
Summary means the router advertise 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 is 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
Here is 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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