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Outer Switches in Enterprise Internet Edge Design

sumesh.nair
Level 1
Level 1

Hi Folks

Seek to know what purpose do the outer switches(Layer two switches between the Internet Router and Firewall) serve as depicted in the 

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/Internet_Edge/InterEdgeOver.html#wp72110

Know that it acts as a Layer 2 Boundary but what functionality/design aspect would one lose/suffer if the firewall and the router are connected back to back

Regards

Sumesh

2 Replies 2

johnd2310
Level 8
Level 8

Hi,

If you read down that documents you find the following under Routing and Switching section:

"As illustrated in Figure 7, the outer switches implement a single Layer 2 segment or VLAN that provides connectivity between the firewalls and the edge routers. This VLAN is the firewall's outside segment. As firewall failover requires all firewall interfaces to be Layer 2 adjacent, the outside VLAN needs to be carried by both outer switches."

Highlighted section would be one of the reasons you have the outer switches.

Thanks

John

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Not sure about that John coz there are designs/implementations in which firewall can be connected back to back with the edge routers.If I am not wrong I can still have all the interfaces as layer 2 adjacent without necessarily having outer switches

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