Solved: EIGRP Network Command

rich_foster · ‎04-25-2010

I've noticed that in 12.4(24)T3 when using the network command in EIGRP it also advertises static routes. For example in my lab I issued the following commands:

router eigrp 1
network 88.0.0.0

ip route 88.0.0.0 255.0.0.0 Null0

And can see the route appear and disappear on a neighboring EIGRP router (as I delete and re-apply the static route):

R8#sh ip eigrp topology 88.0.0.0 255.0.0.0
IP-EIGRP (AS 1): Topology entry for 88.0.0.0/8
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 33280
Routing Descriptor Blocks:
70.15.1.17 (FastEthernet3/0), from 70.15.1.17, Send flag is 0x0
      Composite metric is (33280/30720), Route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 300 microseconds
        Reliability is 0/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 3

This obviously isn't a problem, it's just the 12.4T documentation states the following:

When the network command is configured for an EIGRP routing process, the router matches one or more local interfaces. The network command matches only local interfaces that are configured with addresses that are within the same subnet as the address that has been configured with the network command.

http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_i1.html#wp1026909

Is there any reason why this is happening?

Jon Marshall · ‎04-25-2010

rich_foster wrote:
I've noticed that in 12.4(24)T3 when using the network command in EIGRP it also advertises static routes.  For example in my lab I issued the following commands:
router eigrp 1
  network 88.0.0.0
ip route 88.0.0.0 255.0.0.0 Null0
This obviously isn't a problem, it's just the 12.4T documentation states the following:
When the network command is configured for an  EIGRP routing process, the router matches one or more local interfaces.  The network command matches only local interfaces that are configured with  addresses that are within the same subnet as the address that has been  configured with the network command. 
http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_i1.html#wp1026909
Is there any reason why this is happening?

Richard

The static route you have is pointing to a directly connected interface on the router ie. null0. Because of this and because your network statement covers the static route EIGRP will then advertise this route to it's neighbors. This is not just 12.4T, this is standard EIGRP behaviour.

If you are interested in the gory details, we had a thread on this a while back -

eigrp static route to directly connected interface

Jon

View solution in original post

Jon Marshall · ‎04-25-2010

rich_foster wrote:
I've noticed that in 12.4(24)T3 when using the network command in EIGRP it also advertises static routes.  For example in my lab I issued the following commands:
router eigrp 1
  network 88.0.0.0
ip route 88.0.0.0 255.0.0.0 Null0
This obviously isn't a problem, it's just the 12.4T documentation states the following:
When the network command is configured for an  EIGRP routing process, the router matches one or more local interfaces.  The network command matches only local interfaces that are configured with  addresses that are within the same subnet as the address that has been  configured with the network command. 
http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_i1.html#wp1026909
Is there any reason why this is happening?

Richard

The static route you have is pointing to a directly connected interface on the router ie. null0. Because of this and because your network statement covers the static route EIGRP will then advertise this route to it's neighbors. This is not just 12.4T, this is standard EIGRP behaviour.

If you are interested in the gory details, we had a thread on this a while back -

eigrp static route to directly connected interface

Jon

rich_foster · ‎04-25-2010

Yes it is quite a long thread! It's exactly what I need to know though - thanks for the quick response.