RE: IS-IS Error (FRR)

[<adamv0025 () netconsultings com>]

Interesting, so it is an MTU problem after all, I take it there’s no way to adjust the BPF (Berkeley Packet Filter) 
limit to let the 6020B sized PSNPs through?

 

adam

 

From: Mark Tinka <mark.tinka () seacom mu> 
Sent: Sunday, April 19, 2020 1:47 AM
To: Tony Li <tony1athome () gmail com>; adamv0025 () netconsultings com
Cc: nanog () nanog org
Subject: Re: IS-IS Error (FRR)

 

So we've been discussing this on Slack.

It seems the packet handlers for IS-IS in FRR and how they work on FreeBSD is not completely optimized (not an issue on 
Linux).

FRR-based IS-IS on FreeBSD is sending PSNP's that are 6,020 bytes large. However, FreeBSD's BPF (Berkeley Packet 
Filter) has a packet data limit of 4,096 bytes. This is what is causing the error.

While it is possible to set the IIH MTU in FRR with the "lsp-mtu" command, there is not way to set the PSNP MTU.

In short, IS-IS on FRR does not understand that there is an MTU limit for PSNP's on FreeBSD.

I'm working with the IS-IS FRR team, but as of now, no idea on if/when there will be a fix for this.

While routes are being successfully exchanged between FRR and Cisco IOS XE for IS-IS, this is a show-stopper! So for 
the moment, I cannot recommend anyone runs IS-IS on FRR in production.

As it stands, it appears that this is the only thing standing in the way of a successful deployment, as far as simple 
Anycast services go.

Will keep you all posted as this develops.

Mark.

On 18/Apr/20 16:34, Tony Li wrote:

 

No, IIH’s are padded, hot PSNP’s.

 

Tony





On Apr 18, 2020, at 3:08 AM, adamv0025 () netconsultings com <mailto:adamv0025 () netconsultings com>  wrote:

 

Just shooting in the dark, Isn’t the PSNP padded to some ISIS defined max MTU and that somehow fails due to mismatch on 
em0 L2 MTU?

 

adam

From: NANOG  <mailto:nanog-bounces () nanog org> <nanog-bounces () nanog org> On Behalf Of Mark Tinka
Sent: Friday, April 17, 2020 11:05 AM
To: nanog () nanog org <mailto:nanog () nanog org> 
Subject: IS-IS Error (FRR)

 

Hi all.

I'm almost there getting IS-IS to work without issue. I'm now faced with the following error log:

2020/04/17 10:02:01 ISIS: IS-IS bpf: could not transmit packet on em0: Input/output error
2020/04/17 10:02:01 ISIS: [EC 67108865] ISIS-Snp (1): Send L2 PSNP on em0 failed

This repeats every second.

Anyone know what this could be?

Systems is FreeBSD-12.1-RELEASE-p3.

Despite the error, IS-IS is running and routing is good, talking to a Cisco IOS XE implementation on the other side. So 
the error is throwing me off.

No feedback from the Slack feed, Google doesn't say much, and waiting to hear back from the FRR list.

Mark.