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New Member

31-bit prefix for point to point links


My plans are to run Routed acces in my LAN, However that requires lot of addresses so thought of using 31-bit prefixes. Now I am facing a problem. After using 31-bit prefixes in my point to point interfaces, those IP addresses dont ping at all from each other.

I am also running EIGRP in these devices and I am continuously getting the following errors.

"Neighbor a.b.c.d not on common subnet for GigabitEthernet1/0/2"

I am using Catalyst 6509 running Version 12.2(18)SXF10, Catalyst 3750 and 7206VXR

I know that catalyst 6509 with 12.2(18)SXF10 supports 31-bit mask, however not sure if Catalyst 3750 supports the same.

Can somebody help me know if Catalyst 3750 supports 31-bit mask and which IOS do i need to use for the same?

Thanks in advance


  • Network Management

Re: 31-bit prefix for point to point links

While technically you can do that, its not common practice. Common practice is /30 for point to point networks which leaves the standard network number and broadcast addresses intact and the host addresses seperate.

New Member

Re: 31-bit prefix for point to point links

Thanks for your reply

But I have read this document multiple times. Probably you have not read my question properly...

I wanna know, if Catalyst 3750 switches support 31-bit prefix and if they do what IOS code needs to be run on them?



Re: 31-bit prefix for point to point links

As of 12.4 the only supported platforms listed are:

?Catalyst 2900

?Catalyst 2900XL

?Catalyst 4000 series

?Catalyst 5000 family switches with an installed Route Switch Module

?Catalyst 6000

?Catalyst 8500 series

?Cisco 800 series

?Cisco 1000 series

?Cisco1400 series

?Cisco 1600 series

?Cisco 1700

?Cisco 2600 series

?Cisco 3600 series

?Cisco 4000 series

?Cisco 6400 series

?Cisco 7000 series

?Cisco 8500 series

?Cisco 12000 series

?Cisco MC3810

?Cisco uBR900 series

?Cisco uBR7200

?LightStream 1010 series

thats from the master IOS configuration guide.

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