July 5, 2013 at 02:22 #2931
I’ve noticed that under the section for EIGRP it is stated “Ensure there is no loss of connectivity or suboptimal routing.”
R4 and R6 are not allowed to accept updates from one another, but still want to maintain their neighborship. Therefore, you cannot use the neighbor command. Ensure R4 and R6 ignore all updates from one another, but continue to listen to R2. Ensure there is no loss of connectivity or suboptimal routing. Hint: You will have to configure all three routers.
When I throw up the final configs I see this:
R4#show ip route | i 188.8.131.52
D 184.108.40.206 [90/158720] via 192.168.246.2, 00:01:41, FastEthernet0/0
The next hop is 192.168.246.2 and not 192.168.246.6
Is this technically suboptimal routing? Because it’s ethernet the ARP will come back for R6’s F0/0 interface so technically although the next hop address is 192.168.246.2 it’s still going directly to R6
R4#show ip arp
Internet 192.168.246.6 3 c207.1504.0000 ARPA FastEthernet0/0
R6#show interfaces f0/0
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is c207.1504.0000 (bia c207.1504.0000)
I’m thinking the requirement for suboptimal routing is technically met (and not even really an issue). But we can fix the next hop address by typing “no ip next-hop-self eigrp 2467”
But that might introduce other issues.July 5, 2013 at 03:54 #5488
Another “sub optimal routing” instance that I noticed is under Phase 7: Redistribution
“Mutually redistribute between EIGRP 2467 and OSPF on R2, R6, R4, and R7. Ensure no loops or suboptimal routing occurs.”
When I look at R7 I see:
R7#show ip route | i 220.127.116.11
D 18.104.22.168 [90/2300416] via 192.168.1.4, 00:58:48, Serial1/0
Where R7 can also get to 22.214.171.124 via Fa0/0 (all ethernet on the way) through R1 to R2
OSPF is getting 126.96.36.199 via redistribution so it’s distance is 130 where as in EIGRP it’s a distance of 90 because it’s internal.
If I disable the EIGRP relationship to R4 on R7 ( no neighbor 192.168.1.4 Serial1/0 ) I can see the path change back to F0/0
If OSPF is preferred through the distance command we can get all the way to R6 via ethernet (optimal?):
R7(config-router)#do trace 188.8.131.52
Type escape sequence to abort.
Tracing the route to 184.108.40.206
1 192.168.157.1 84 msec 108 msec 8 msec
2 192.168.123.2 144 msec 172 msec 108 msec
3 192.168.246.6 304 msec * 292 msec
BUT if OSPF is preferred and we kill F0/0 all of the routes then go through R1 instead of R4 (such as when going to R6 @ 220.127.116.11) and that seems suboptimal since R4 and R6 are directly connected where as R1 has to go through R2.
I’m not that great with the whole redistribution thing so I can’t really come up with a good way to get optimal routing with both OSPF and EIGRP enabled and maintaining optimal routing when a link dies 😀July 5, 2013 at 13:52 #2932
These are both excellent findings. I did not consider them when making the lab.August 17, 2015 at 11:06 #24701
I do not see the GNS3 file, can you please advise?
Thanks in advance.
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