Limitations with the number of software interfaces ?

Answered Question
Jun 1st, 2007

Hello,

I have to configure about 5k tunnel and additional 5k loopback interfaces on 7301 and 7206VXR (NPE-G1). We are running 12.2 SB and 12.4 Mainline.

Are there any limitations regarding a max. number of tunnel and/or loopback interfaces in above versions ? The former limitation was 255 tunnel interfaces, but now I can assign numbers up 2 billion.

Best regards,

Stephan

I have this problem too.
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Correct Answer by mohammedmahmoud about 9 years 7 months ago

Hi Stephan,

Rick is totally right, the limitation of the interfaces is bind to the IDB limit which is a function of the IOS and the Platform.

Each tunnel interface definition, such as Universal Transport Interface (UTI), Generic Routing Encapsulation (GRE), Multiprotocol Label Switching Traffic Engineering (MPLS TE), or Any Transport over MPLS (AToM) consumes an HWIDB plus one SWIDB per tunnel, plus an additional SWIDB for each additional sub-interface, for example, a Frame Relay PVC, that is tunneled. The tunnel IDBs are in addition to the original interface(s) that are tunneled.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_tech_note09186a0080094322.shtml

Following is the output of one of our G1s running a 12.3 code.

7206-G1#show idb

Maximum number of Software IDBs 20050. In use 1568.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

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Richard Burts Fri, 06/01/2007 - 09:25

Stephan

I believe that the limitation that you will encounter is the limitation on IDBs (Interface Descriptor Blocks). Each interface (whether hardware or software) requires an IDB. The number of IDBs has changed in various releases (and may vary by feature set and/or platform - I am not sure about that). I have a 7206VXR running 12.4 mainline (Advanced Security feature set) which has a limit of 20050 IDBs. You can use the show idb command on your platforms to see what the limits will be on your gear.

HTH

Rick

Correct Answer
mohammedmahmoud Fri, 06/01/2007 - 12:48

Hi Stephan,

Rick is totally right, the limitation of the interfaces is bind to the IDB limit which is a function of the IOS and the Platform.

Each tunnel interface definition, such as Universal Transport Interface (UTI), Generic Routing Encapsulation (GRE), Multiprotocol Label Switching Traffic Engineering (MPLS TE), or Any Transport over MPLS (AToM) consumes an HWIDB plus one SWIDB per tunnel, plus an additional SWIDB for each additional sub-interface, for example, a Frame Relay PVC, that is tunneled. The tunnel IDBs are in addition to the original interface(s) that are tunneled.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_tech_note09186a0080094322.shtml

Following is the output of one of our G1s running a 12.3 code.

7206-G1#show idb

Maximum number of Software IDBs 20050. In use 1568.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

s.steiner Sun, 06/03/2007 - 23:00

Hi Rick, Hi Mohammed,

both of you, thank you very much for the detailed answers !!

Best regards,

Stephan

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