HSRP , inter vlan routing, IP CEF

Answered Question
May 12th, 2010
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We have four core sites on our network which have 2 x Cisco 6509s each. The network is predominantly layer 2 with Vlans spanning all four sites.  The sites are connected by a mixture of 100mb and 1GB Lan extension Services(LES).
We have HSRP c onfigured for the Vlans.
My question is :
the HSRP active router for vlan 20 is at site A and the active router for vlan 70 is at site C .
At site C I have a workstation on Vlan 70 located on one switch and a server at site C located on a different switch. If I send traffic between the 2 devices will it travel up to site A to Vlan 20s default gateway to swap Vlans and then back down the link again.

Correct Answer by Jon Marshall about 7 years 1 month ago

smith606306 wrote:


We have four core sites on our network which have 2 x Cisco 6509s each. The network is predominantly layer 2 with Vlans spanning all four sites.  The sites are connected by a mixture of 100mb and 1GB Lan extension Services(LES).
We have HSRP c onfigured for the Vlans.
My question is :
the HSRP active router for vlan 20 is at site A and the active router for vlan 70 is at site C .
At site C I have a workstation on Vlan 70 located on one switch and a server at site C located on a different switch. If I send traffic between the 2 devices will it travel up to site A to Vlan 20s default gateway to swap Vlans and then back down the link again.


Andrew


Is the server in vlan 20 ?


If so the client in vlan 70 will send the traffic to it's default-gateway which is at site C. The packet will then be routed onto vlan 20 by the switch at site C and sent to the server in site C. So the traffic does not need to go to site A.


However return traffic will because the server in site C has it's default-gateway in site A so the traffic will go to main switch in site C be switched across the link to site A vlan 20 SVI, be routed onto vlan 70 by site A switch and then sent back across the link to the client in vlan 70.


Jon

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Correct Answer
Jon Marshall Wed, 05/12/2010 - 12:13
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smith606306 wrote:


We have four core sites on our network which have 2 x Cisco 6509s each. The network is predominantly layer 2 with Vlans spanning all four sites.  The sites are connected by a mixture of 100mb and 1GB Lan extension Services(LES).
We have HSRP c onfigured for the Vlans.
My question is :
the HSRP active router for vlan 20 is at site A and the active router for vlan 70 is at site C .
At site C I have a workstation on Vlan 70 located on one switch and a server at site C located on a different switch. If I send traffic between the 2 devices will it travel up to site A to Vlan 20s default gateway to swap Vlans and then back down the link again.


Andrew


Is the server in vlan 20 ?


If so the client in vlan 70 will send the traffic to it's default-gateway which is at site C. The packet will then be routed onto vlan 20 by the switch at site C and sent to the server in site C. So the traffic does not need to go to site A.


However return traffic will because the server in site C has it's default-gateway in site A so the traffic will go to main switch in site C be switched across the link to site A vlan 20 SVI, be routed onto vlan 70 by site A switch and then sent back across the link to the client in vlan 70.


Jon

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