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Changing routing preference in a EIGRP network between 3 offices

Posted on 2013-06-17
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Last Modified: 2013-06-21
Dear Experts:

I need to change the EIGRP routing preference between offices.

We have office A as the main office with cisco call manager  there among other applications.

There is office B that has the mail server for office C. And there is part of my problem.

I need to make office C discontinue using the VPN tunnel between office B directly. It now needs to come from office A to office B.

Here a traceroute example from office C to office B:

#traceroute 172.16.8.240 <-- office B LAN network address for Mail Server

Type escape sequence to abort.
Tracing the route to officeB mail server (172.16.8.240)

  1 172.16.16.3 0 msec 0 msec 4 msec <-- voice gateway router for office C
  2 10.255.255.13 40 msec 40 msec 36 msec <-- Office B VPN tunnel interface
  3 officeB mail server (172.16.8.240) 40 msec 44 msec 44 msec
 #

I need it to be as follows:


#traceroute 172.16.8.240

Type escape sequence to abort.
Tracing the route to officeB mail server (172.16.8.240)

  1 10.255.255.17 32 msec 32 msec 32 msec <-- office A router
  2 AT & T IP Flex network to LAN network Office B
  4 officeB mail server (172.16.8.240) 100 msec 108 msec 104 msec

 

Traffic right now from office A to office B travels through Office C tunnel. While traffic from office B to office A is the way it should be not over the VPN tunnel but over the AT& T IP flex connection. Another issue.

The VPN tunnel between Office B and C is going to end. So I need to make the routing changes so office A and B does not travel through Office c and office c gets to office B through office A.

The networks needed to be reached are as follow:
Office A 172.16.102.0, 172.16.100.0 172.16.104.0
Office B 172.16.10.0, 172.16.8.0, 172.16.12.0
Office C 172.16.16.0, 172.16.17.0

Attached  is a drawing I made.
ntwrktopology2.jpg
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Comment
Question by:marceloNYC
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6 Comments
 
LVL 17

Expert Comment

by:surbabu140977
ID: 39255260
After seeing your diagram and your question, I have only one question(answer) for you.

If VPN between B -C is ending, why do you need to bump your head with routing? EIGRP will fall back instantly i.e EIGRP will see that only way to reach B (from C) is through A and it will take that path automatically.

If,
You want to keep the tunnel between B and C now and still want to pass traffic through A and B (from C), you just look at the eigrp topology table in C. You are likely to see one more route (not in routing table) in the topology table of EIGRP database pointing to B through router A. (metric will be higher).

If you see that, just adjust the metric so that it comes below the present B-C path. Traffic will start flowing between A and B(for C) ignoring B-C path.

If you do not see that path, then use "variance" command in EIGRP, you will be able to control the traffic flow through A-B instead of B-C.

I am assuming you are quite familiar with EIGRP operations and should be able to figure out what I am saying.
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LVL 17

Expert Comment

by:surbabu140977
ID: 39255266
You can actually test it by shutting down the tunnel between B and C, and you will see traffic start flowing through A (from C towards B). If it does not, then you have a problem in EIGRP routing. EIGRP fallback is always automatic and one of the easiest protocol to deal.
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Author Comment

by:marceloNYC
ID: 39256196
That's the problem is not going back to static routing between office B and A. If i shutdown the tunnel between office B and C I and not able to get the Off A from office B
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Author Comment

by:marceloNYC
ID: 39256240
If I turn off the Tunnel between office C I have office B totally disconnected from everything.

sh ip route eigrp

D    192.168.10.0/24 [90/4596224] via 10.255.255.14, 09:46:55, Tunnel40 <tunnel40
     172.16.0.0/16 is variably subnetted, 11 subnets, 3 masks
D       172.16.16.0/23 [90/4340224] via 10.255.255.14, 09:46:55, Tunnel40
D       172.16.19.0/24 [90/4852224] via 10.255.255.14, 09:46:55, Tunnel40
D       172.16.8.0/22 is a summary, 09:46:58, Null0
D       172.16.104.0/24 [90/4596224] via 10.255.255.14, 09:46:55, Tunnel40
D       172.16.100.0/22 [90/4596224] via 10.255.255.14, 09:46:55, Tunnel40
     172.31.0.0/16 is variably subnetted, 3 subnets, 2 masks
D EX    172.31.238.8/30 [170/4598784] via 10.255.255.14, 09:46:55, Tunnel40
D EX    172.31.238.4/30 [170/4598784] via 10.255.255.14, 09:46:55, Tunnel40
     10.0.0.0/8 is variably subnetted, 12 subnets, 4 masks
D       10.255.255.8/30 [90/4593664] via 10.255.255.14, 09:46:55, Tunnel40
D EX    10.255.254.0/30 [170/4598784] via 10.255.255.14, 09:46:55, Tunnel40
D EX    10.255.254.4/30 [170/4598784] via 10.255.255.14, 09:46:55, Tunnel40
D       10.255.255.16/30 [90/4849664] via 10.255.255.14, 09:46:55, Tunnel40
D       10.255.0.1/32 [90/4721664] via 10.255.255.14, 09:46:55, Tunnel40
D       10.255.0.2/32 [90/4724224] via 10.255.255.14, 09:46:55, Tunnel40
D       10.255.0.12/32
           [90/156160] via 172.16.10.3, 09:38:43, FastEthernet1.222
D       10.255.0.14/32 [90/4977664] via 10.255.255.14, 09:46:55, Tunnel40
is-okc-rtvpn-01#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
 router B(config)#int
 router B(config)#interface tunn
 router B(config)#interface tunnel 40
 router B(config-if)#shut
 router B(config-if)#exit
 router B(config)#exit
 router B#sh ip route eigrp
     10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
D       10.255.0.12/32
           [90/156160] via 172.16.10.3, 09:39:36, FastEthernet1.222


 router B#ping 172.16.100.240

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.100.240, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
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LVL 17

Accepted Solution

by:
surbabu140977 earned 500 total points
ID: 39256444
You do not have a feasible successor in EIGRP for office C. In the EIGRP topology table of C (not routing table) you should see 2 paths to reach B.One through A and the other directly to B.

If you cannot see 2 paths, you have to manipulate the path cost to make it a feasible successor. Once you see 2 paths, then this problem should be over. One shut down the other then takes over.

This is achievable by manual setting of path cost or/and using variance command. You need to read a bit about EIGRP to get this work. Nothing complicated.

Best,
0
 

Author Closing Comment

by:marceloNYC
ID: 39267048
Well as it turned out the solution was in AT&T IP Flex network to allow the traffic between offices. We had to declare all of our LAN networks to them.

I thank you for your helpful information on the EIGRP protocol.

Regards, M
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