RIP vs EIGRP - passive interfaces and neighbor statement

joetest

Ran into some strange stuff with EIGRP and RIP. Perhaps not but whatever

Maybe I'm just overthinking this.
Scenario:


And 4 different tests - 2 with RIP and 2 with EIGRP:


############## RIP test 1 with passive-interface only on R6
R6#sh run | s router rip
router rip
timers basic 10 20 15 20
passive-interface Ethernet0/0
network 10.0.0.0
network 192.168.1.0
R6#sh ip route rip
R 192.168.2.0/24 [120/1] via 10.0.1.7, 00:00:08, Ethernet0/0

R7#sh run | s router rip
router rip
timers basic 10 20 15 20
network 10.0.0.0
network 192.168.2.0
R7#sh ip route rip

R7#
Pretty much expected behavior - R7 doesn't get the 192.168.1.0/24 network, because R6 doesn't send it.

---

################# RIP test 2 with neighbor and passive-interface cmd:
R6#sh run | s router rip
router rip
timers basic 10 20 15 20
passive-interface Ethernet0/0
network 10.0.0.0
network 192.168.1.0
neighbor 10.0.1.7
R6#sh ip route rip
R 192.168.2.0/24 [120/1] via 10.0.1.7, 00:00:09, Ethernet0/0
R6#

R7#sh run | s router rip
router rip
timers basic 10 20 15 20
network 10.0.0.0
network 192.168.2.0
R7#sh ip route rip
R 192.168.1.0/24 [120/1] via 10.0.1.6, 00:00:02, Ethernet0/0
R7#
Okay, so by using the Neighbor cmd(unicast) you circumvent the Passive-interface(unicasts allowed, but not multicast/broadcast)

---

###### EIGRP test 1 with passive-interface only on R6
R6#sh run | sec router eigrp
router eigrp 1
passive-interface Ethernet0/0
network 10.0.0.0
network 192.168.1.0
no auto-summary
R6#sh ip route eigrp

R6#

R7#sh run | sec router eigrp
router eigrp 1
network 10.0.0.0
network 192.168.2.0
no auto-summary
R7#sh ip route eigrp

R7#
Expected behavior - Passive-interface stops the sending of updates and Hellos so no neighbor relationship can exist

---

########## EIGRP test 2 with passive-interface on R6 and neighbor cmds on both for unicast behavior
R6#sh run | sec router eigrp
router eigrp 1
passive-interface Ethernet0/0
network 10.0.0.0
network 192.168.1.0
no auto-summary
neighbor 10.0.1.7 Ethernet0/0
R6#sh ip route eigrp

R6#

R7#sh run | sec router eigrp
router eigrp 1
network 10.0.0.0
network 192.168.2.0
no auto-summary
neighbor 10.0.1.6 Ethernet0/0
R7#sh ip route eigrp

R7#
Zip, nada, nothing.. So neighbor statements circumvents Passive-interface on RIP by sending updates as unicast but still blocks EIGRP Hello packets from being sent even though they're unicast packets?

This is actually a thing or do I misunderstand something? Perhaps useless observation but it got me wondering

OfWolfAndMan

The passive interface command with RIP is a little different. It won't send multicast updates but unicast is still fair game. Also, RIP will still listen to updates sent by other RIP routers.

AwesomeGarrett

That is the intended behavior.

Danman32

I just looked up passive-interface on EIGRP, where I came up with a cisco doc on the issue.
Passive-interface suppresses hellos. No hellos, no neighbor relationship. No neighbor relationship, no route exchange in either direction.
Although EIGRP is considered a distance vector routing protocol, much of its characteristics is behavior much like a link-state in the sense a router has much of the routing information of the network.
RIP on the other hand just pushes route information, without much handshaking.

joetest

Danman32 wrote: »

I just looked up passive-interface on EIGRP, where I came up with a cisco doc on the issue.
Passive-interface suppresses hellos. No hellos, no neighbor relationship. No neighbor relationship, no route exchange in either direction.
Although EIGRP is considered a distance vector routing protocol, much of its characteristics is behavior much like a link-state in the sense a router has much of the routing information of the network.
RIP on the other hand just pushes route information, without much handshaking.

That's pretty much what I wrote. It was the neighbor cmd that made me wonder