Network Dualism

Answered Question
Mar 30th, 2009
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Hi All.


I have sw1 for core-switch. and sw2 for standby. both are multi-layer switches.


As I know , to make dualism, need to use HSRP. My question is that Can I use HSRP in Multi-layer switches? or is it only functioned in Router? Do you know good way to make dualism?

Correct Answer by Giuseppe Larosa about 7 years 12 months ago

Hello Lee,

yes you can use HSRP on multilayer switches we do it on all our campus networks.


However, there is one important note about HSRP implementation that needs to be taken in account:

in routers Vlan based subinterfaces like fas0/0.100, fas0/0.110 and so on require to use different HSRP group number on each of them.

Multilayer switches can use the same HSRP group on multiple SVI Vlan interfaces.

Actually for multilayer switches this is a scalability feature: with the exception of C6500 other platforms can support a low number of HSRP group numbers for example 16 but allow to reuse them as needed:

so you can have 16 different groups but used in 160 different Vlans.


Multilayer switches are able to track on what vlan a packet is received.


Depending on the platform if supported you may also consider GLBP that provides effective load balancing for vlans where multiple clients are present


Hope to help

Giuseppe


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Correct Answer
Giuseppe Larosa Mon, 03/30/2009 - 01:08
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Hello Lee,

yes you can use HSRP on multilayer switches we do it on all our campus networks.


However, there is one important note about HSRP implementation that needs to be taken in account:

in routers Vlan based subinterfaces like fas0/0.100, fas0/0.110 and so on require to use different HSRP group number on each of them.

Multilayer switches can use the same HSRP group on multiple SVI Vlan interfaces.

Actually for multilayer switches this is a scalability feature: with the exception of C6500 other platforms can support a low number of HSRP group numbers for example 16 but allow to reuse them as needed:

so you can have 16 different groups but used in 160 different Vlans.


Multilayer switches are able to track on what vlan a packet is received.


Depending on the platform if supported you may also consider GLBP that provides effective load balancing for vlans where multiple clients are present


Hope to help

Giuseppe


Joseph W. Doherty Mon, 03/30/2009 - 04:24
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As Giuseppe notes, yes Cisco L3 switches might support HSRP. However, they might not support as many as the typical routers. For instance, the original 3750s is documented by Cisco in http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5023/prod_qas09186a00801b0971.html as:


Q. How many HSRP groups does the Cisco Catalyst 3750 Series support?

A. The Cisco Catalyst 3750 Series supports up to 32 HSRP groups.


PS:

Other gateway protocols, GLBP and VRRP, might be supported too.

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