From: Joseph Brunner (joe@affirmedsystems.com)
Date: Sat Apr 12 2008 - 00:10:07 ART
<crap removed>
1.) EIGRP split-horizon
Understand that this is on by default, is there any commands to verify if
the EIGRP split-horizon is on?
Not that I can tell... but I'm known to occasionally miss things...
2.) What happens a EIGRP is running on a FrameRelay? Split-horizon is
disabled by default on the Main Interface of FrameRelay interface, which
will takes precedence? EIGRP (Split-horizon on by default), FrameRelay main
interface (Split-horizon off by default)?
Well, consider my lab topology...
R5, R6, and R7 with R5 as the hub, running physical interface frame-relay
using map commands
R6 and R7 are advertising their F0/0 subnets to R5, the hub.
R5#show ip route eigrp
172.17.0.0/24 is subnetted, 2 subnets
D 172.17.17.0 [90/2195456] via 1.56.7.7, 00:00:19, Serial1/0
D 172.17.16.0 [90/2195456] via 1.56.7.6, 00:00:37, Serial1/0
Now, without split horizon disabled for eigrp on R5...
R6 and R7 don't get each other's F0/0 Subnet via EIGRP
R6#show ip route eigrp
R7#show ip route eigrp
Now, I disable EIGRP split horizon on R5
R5(config)#int s1/0
R5(config-if)#no ip split-horizon eigrp 10
And R6, and R7 see...
R6#show ip route eigrp
172.17.0.0/24 is subnetted, 2 subnets
D 172.17.17.0 [90/2707456] via 1.56.7.5, 00:00:46, Serial1/0
R7#show ip route eigrp
172.17.0.0/24 is subnetted, 2 subnets
D 172.17.16.0 [90/2707456] via 1.56.7.5, 00:00:59, Serial1/0
EACH OTHER'S F0/0 Subnet!!!!
So Eigrp does indeed have final say over which interfaces run split horizon
or not...
3.) EIGRP auto-summary
with auto-summary, it is always pointing to null0?
Unless you raise the AD to 255 in the summary's route command...
(My R6)
R6(config-if)#ip summary-address eigrp 10 172.17.16.0 255.255.252.0 255
Then its NOT in the routing table AT ALL (no loop prevention!!!)
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