EIGRP static route redistribution config logic?

[jmaxwellUSAF]

Hello.

In the below config designed to

redistribute

static routes into EIGRP...

1. What is the significance of

access-list

10 to the

route map

and the

redistribution

config? (it only has the IP address of a monitoring server. (?))

2. May you please clarify my understanding here of the EIGRP

redistribution

config logic? My understanding is that ACL 10 is what is referenced by the

route map

In this example this ACL seems to be irrelevant and ignored, in preference to the

prefix-list

Thank you.

=====

(obfuscated)




CAT_9300_x4#sh run | s eigrp

router eigrp 1

!! (output omittted) !!

 network 172.57.0.0

 redistribute static route-map STAT_ROUTE_EIGRP

 auto-summary

-----




CAT_9300_x4#sh route-map STAT_ROUTE_EIGRP

route-map STAT_ROUTE_EIGRP, permit, sequence 10

  Match clauses:

    ip address prefix-lists: STAT_ROUTE_EIGRP 

-----




CAT_9300_x4#sh access-lists 10

Standard IP access list 10

    10 permit 172.59.44.100  !! this is a monitoring server !!

-----




CAT_9300_x4#sh ip prefix-list STAT_ROUTE_EIGRP

ip prefix-list STAT_ROUTE_EIGRP: 16 entries

!! (output omitted) !!

   seq 40 permit 172.56.22.0/24

-----

[M02@rt37]

Hello @jmaxwellUSAF,

The

access-list

10 is used in the

route map

to match specific IP addresses or networks. In this case,

access-list

10 permits the IP address 172.59.44.100, which is identified as a monitoring server.

The

route map named STAT_ROUTE_EIGRP

is configured with a single permit statement (sequence 10) that includes a match clause referencing the

prefix-list STAT_ROUTE_EIGRP

The purpose of this

route map

is to determine which static routes are

redistributed

into EIGRP.

The ACL 10 is referenced by the

 route map

but in this specific example, it seems to be irrelevant and ignored. The reason for this is that the only entry in

access-list

10 permits the IP address 172.59.44.100, which is not included in the

prefix-list STAT_ROUTE_EIGRP

used in the

route map

Therefore, the ACL 10 does not play a role in determining which routes are

redistributed

The

prefix-list STAT_ROUTE_EIGRP

is the primary matching criterion used in the

route map

It defines a list of

prefixes

(IP networks) that are permitted or denied for

redistribution

into EIGRP. In this case, the

prefix-list

permits the IP network 172.56.22.0/24.

[David Ruess · Accepted solution]

Not quite. The ACL is NOT referenced in the

route-map

only the

Prefix list

is. Here is the logic:

 redistribute static route-map STAT_ROUTE_EIGRP <- this redistributes static routes but only routes referenced in the route map

route-map STAT_ROUTE_EIGRP, permit, sequence 10 <- 10 is the sequence number of the route-map not the ACL #

  Match clauses:

    ip address prefix-lists: STAT_ROUTE_EIGRP  <-this matches the prefix list called STAT_ROUTE_EIGRP

ip prefix-list STAT_ROUTE_EIGRP: <- this defines what networks are in the prefix list

   seq 40 permit 172.56.22.0/24 <- this is the network that will be matched on in the route-map 

So in this case if you have 100 static routes and you issue the 

redistribute static

command under EIGRP then it will

redistribute

all of the static routes configured on the device. The

route-map

coupled with either an ACL or in this case

prefix-list

will limit which of the static routes actually make it into EIGRP. Its a form of route manipulation.

Its generally better to use a

prefix list

as you can get more granular control for certain network advertisements.

-David

[Giuseppe Larosa]

Hello @jmaxwellUSAF ,

@David Ruess 's answer it totally correct the

route-map

uses sequence numbers for

route-map

blocks / clauses and that 10 is the default sequence number for the first block of the

roue-map

. The

route-map

invokes only the

prefix-list

and only static routes that have a match in one of the

prefix list

statement will be

redistributed

into EIGRP.

IP access-list

10 is not related to the

route-map

Hope to help

Giuseppe