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L2 or L3 link between distribution swithes?

Hi,

we will change our network from L2 to multilayer (L2/L3) network. The layout of the network is the traditional access-distribution-core -type network where the access-distribution link is L2 link and the distribution-core link is L3 link. In the core there is a Cisco 7609 OSR with two gigabit fiber modules and later on we will purchace second 7609 as a redundant router. Distribution switches are Cisco 3750 and access switches are third party products.

I've read throug some Cisco's recommendations about the multilayer layout and there are two different solutions for the link between the distribution switches. One recommendation is to use L2 link and another is to use L3 link. Which is the better way?

-Sami

Reply to
aquarius
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If you post some pointers to documents (and locations in those) documents describing the cases someone may have a look.

The one thing you do not want is unicast flooding.

Reply to
Bod43

The following document has a picture on page 66. There is a L2 link used between distribution switches. In the next page there is a L3 link. It says there that the L2 solution should only be used if layer 2 spanning flexibility is required. What does that "flexibility" mean?

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-Sami

Reply to
aquarius

"aquarius" ha scritto nel messaggio news:%tgBh.48413$ snipped-for-privacy@news2.nokia.com...

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Hi,

VLAN flexibility is this case means the capability to span the same VLAN id among multiple access switched served by the same distribution block, so you need a Layer 2 trunk between distribution switches ( this isn't a recommended design by cisco, unless your data block is a data center or has particular needs )

Obviously if you need to do that you could deploy either a L2 Trunk and a L3 path between distribution switches.

Regards, Gabriele

Reply to
Gabriele Beltrame

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Hi,

yes, we need to use same VLAN id among multiple access switches. Therefore I guess that we have to use L2 link between distribution switches?

-Sami

Reply to
aquarius

"aquarius" ha scritto nel messaggio news:9XcCh.48486$ snipped-for-privacy@news2.nokia.com...

Hi,

yes, it's better to have a L2 trunk then. ( try to have it in (R)STP discarding/blocking state under normal circumstances )

Regards, Gabriele

Reply to
Gabriele Beltrame

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