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Cisco 28xx: VLANs support

Sirs:

What is the maximum number of VLANs allowed in the in-built FEth interfaces? It depends on IOS version?

2 REPLIES
Purple

Re: Cisco 28xx: VLANs support

Hi,

The 2800 platform will allow you to configure any of the VLAN IDs in the range of 1-4094. The number of actual sub-interfaces that you can create will be limited by the number of Interface Descriptor Blocks (IDB) supported by the platform.

Quoting from CCO: "An Interface Descriptor Block (IDB) is a special control structure internal to the Cisco IOS software that contains information such as the IP address, interface state, and packet statistics. Cisco IOS software maintains one IDB for each interface present on a platform and one IDB for each subinterface."

The number of interfaces that you can have is limited by the IDB limit for the platform and of course, memory available.

Therefore, while you can theoretically configure 4094 ethernet sub-interfaces, in practice that is not achievable.

Now, the 2821 supports a maximum of 1400 software IDBs. So that is what you are limited to.

Pls do remember to rate posts.

Paresh

Purple

Re: Cisco 28xx: VLANs support

Just another note: you can use the 'show idb' command to see the max number of IDBs supported on your particular platform.

Cheers,

Paresh

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