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How to test GLBP ?

Unanswered Question
Mar 18th, 2007
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Hi,

We have configured GLBP with round robin configuration. How do we test / check that every alternate request for outbound is processed by tow different routers ?

Ho do we decipher # show glbp command output to see round- robin is working ?

Thanx in advance

Subodh

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cristip Mon, 03/19/2007 - 07:49
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-You can use SNMP ...and ftp sessions to two different targets.

-You can use debug ip packets access-list on each router to see the traffic flowing to each router

-inspecting the arp table on each workstation would shou you what ruter is beeing used by what workstation

-any sniffing (use ethereal it's free) would do it




Darren Ramsey Mon, 03/19/2007 - 08:32
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A very simple method is to traceroute from a workstation on a GLBP segment to a routed destination, and observe the next hop address. Then clear arp on the workstation (windows: arp -d *) and traceroute again. You should see it hit the other GLBP next hop address. Depending on the timing, you might need to clear arp more than once.


Example


C:\>tr fin


Tracing route to fin-primary.wellmont.org [172.16.4.100]

over a maximum of 30 hops:


1 <1 ms <1 ms <1 ms corp-core1-4.wellmont.org [10.1.4.2]

2 <1 ms <1 ms <1 ms brmc-core1-gi1/1.wellmont.org [192.168.200.6]

3 <1 ms <1 ms <1 ms fin-primary.wellmont.org [172.16.4.100]


Trace complete.


C:\>arp -d *


C:\>tr fin


Tracing route to fin-primary.wellmont.org [172.16.4.100]

over a maximum of 30 hops:


1 <1 ms <1 ms <1 ms corp-core2-4.wellmont.org [10.1.4.3]

2 <1 ms <1 ms <1 ms brmc-core2-gi1/1.wellmont.org [192.168.200.106]


3 <1 ms <1 ms <1 ms fin-primary.wellmont.org [172.16.4.100]


Trace complete.

Trony Fri, 03/30/2007 - 08:22
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I tested my glbp config by first noting down the mac address of the router in the arp table on my laptop, clearing the arp table, and checking it again. The mac address changed to the backup router. I did this a few times and it flipped back and forth at every instance.

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