topic Re: /31 netmask in ExtremeSwitching (VSP/Fabric Engine)

/31 netmask

Antero_Vasconce — Wed, 21 Jul 2021 17:06:05 GMT

i am trying to configure a /31 address in VSP 7400 rel 8.6 but always gives error.

“brouter port 1/54 vlan XXXX subnet XXX.YYY.ZZZ.153 255.255.255.254”

“port 1/54, Invalid IP address”

is this possible or not on VSP?

thanks in adv

Antero

Re: /31 netmask

Ludovico_Steven — Wed, 21 Jul 2021 17:09:57 GMT

31 bit masks are not supported with VOSS. You’ll need to allocate a 30 bit mask.

Re: /31 netmask

Antero_Vasconce — Wed, 21 Jul 2021 21:59:37 GMT

that is a very bad news.

do you know when it will be available?

for interconnecting with ISP with BGP this is a huge problem.

thanks

Antero Vasconcelos

Re: /31 netmask

EXTR_Paul — Thu, 22 Jul 2021 04:44:44 GMT

that is a very bad news.

FYI…..

31 bit network masks as specified by RFC3021 is not an internet standard. https://datatracker.ietf.org/doc/html/rfc3021 It is only a “proposed standard”.

Re: /31 netmask

Ludovico_Steven — Thu, 22 Jul 2021 20:55:08 GMT

You might be able to swing it this way..

If the WAN IP address ends in 01 or 10 binary, then simply create the VSP IP ending with 10 or 01 binary (the other way round) but using a /30 mask.

If the WAN IP address ends in 00 or 11 binary, then it’s more fiddly..!

Re: /31 netmask

bfaltys — Thu, 16 Sep 2021 20:45:15 GMT

A /31 really has no use as the first IP would be the network address and the 2nd would be the broadcast address. That leaves 0 addresses for you to assign to your brouter port. At a minimum you will need a /30 as recommended. That leaves 2 IPs for hosts/brouters etc.

Re: /31 netmask

Tomasz — Tue, 21 Sep 2021 16:35:00 GMT

Hi,

Some vendors and even Extreme platforms (EXOS or SLX AFAIR, but not VOSS) support /31 where for L3 point-to-point there’s no actual need for network/bcast IP, but IMHO it only makes sense when dealing with a constrained pool of public IPs. Other than that, and minding that /31 is not a standard, it should be possible to discuss and get things straight with the peer service provider.

Cheers,

Tomasz

Re: /31 netmask

Samuel_Knutti — Wed, 19 Feb 2025 09:02:50 GMT

Hi Ludovico,

your answer is 4 years and some major releases old. Is it still not supported?

regards,

Samuel