09-17-2009 07:49 AM - edited 03-04-2019 06:05 AM
Imagine I have the following:
CorporateRouter1-------(S0/0)EIGRP-STUB-BranchRouter
Advertising:172.16.1.0/24
192.168.1.0/24
10.0.0.0/24
CorporateRouter2-------(S0/1)EIGRP-STUB-BranchRouter
Advertising:10.0.0.0/24
192.168.1.0/24
Let's say that due to a misconfiguration, 172.16.1.0/24 is not being advertised on CorporateRouter2.
So both Corporate Routers connected to the branch office EIGRP-Stub routers.
Let's say CorporateRouter1 dies for good. Since we have a stub configured on EIGRP-STUB-BranchRouter, the branch router will not query CorporateRouter2 in order to learn route 172.16.1.0/24 no matter what, right?
Solved! Go to Solution.
09-17-2009 01:37 PM
Hello Rick,
Are you sure about this? I have a different experience and the debug eigrp packet update query reply confirms that: while a stub router routinely answers with destination unreachable to all queries, the stub functionality does not prevent it from sending queries itself.
I could provide some debugs here but I don't want to do it right now. I'd like to just highlight another thread where this topic was also discussed:
Best regards,
Peter
09-17-2009 07:56 AM
Marlon
There are some details in your question that are not clear to me, especially about the possible configuration error. But it is clear that the effect of configuring the Branch router as a stub is that if it loses a route that it learned then it will not generate a query for that route.
HTH
Rick
09-17-2009 01:37 PM
Hello Rick,
Are you sure about this? I have a different experience and the debug eigrp packet update query reply confirms that: while a stub router routinely answers with destination unreachable to all queries, the stub functionality does not prevent it from sending queries itself.
I could provide some debugs here but I don't want to do it right now. I'd like to just highlight another thread where this topic was also discussed:
Best regards,
Peter
09-17-2009 08:22 PM
Peter, no problem after this excellent explanation I took the time to build the lab and verify this; Yes I can see that once I shut the connection between CorporateRouter1 to the Stub router(R3 below) the second Corporate Router receives a QUERY from the stub router. Perfect! Thanks all.
R1#debug eigrp packets reply
EIGRP Packets debugging is on
(REPLY)
R1#debug eigrp packets query
EIGRP Packets debugging is on
(QUERY)
R1#
00:25:52: EIGRP: Received QUERY on FastEthernet1/0 nbr 192.168.1.3
00:25:52: AS 100, Flags 0x0, Seq 24/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely
0/0
R3#debug eigrp packets query
EIGRP Packets debugging is on
(QUERY)
R3#debug eigrp packets reply
EIGRP Packets debugging is on
(REPLY)
R3#
R3#ping 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 48/90/120 ms
R3#config t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#
R3#
00:20:20: %SYS-5-CONFIG_I: Configured from console by console
00:20:48: EIGRP: Received REPLY on FastEthernet1/0 nbr 192.168.1.1
00:20:48: AS 100, Flags 0x0, Seq 9/24 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely
0/0
R3#show ip route
09-18-2009 07:12 AM
Peter and Marlon
Thank you for improving my understanding of EIGRP stub. Sorry that my initial response was off the mark. It is always good to learn things and improve understanding on the forum.
HTH
Rick
09-18-2009 11:02 AM
Hello Rick,
You are heartily welcome, and absolutely no apologies are necessary. And I'm sure I am going to learn a lot from you.
Best regards,
Peter
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