[j-nsp] OSPF MTU-IGNORE?

[Arda Balkanay]

The answer is "no" for setting mtu-ignore in juniper
side.
You can set the mtu in juniper to match with the cisco
but this may have a bad effect on your mpls network
(for jumbo frames). In cisco side you can configure
mpls mtu like:

interface FastEthernet9/1/1
 ip address my_ip_address
 duplex auto
 speed auto
 mpls ip
 mpls mtu 1550
 mpls traffic-eng tunnels
 no cdp enable
 ip rsvp bandwidth 100000
end
and mpls mtu and ip mtu is shown as:
XYZ#sh int fa 9/1/1
...
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
...
XYZ#show mpls interfaces fastEthernet 9/1/1 detail
Interface FastEthernet9/1/1:
        IP labeling enabled (ldp):
          Interface config
        LSP Tunnel labeling enabled
        BGP tagging not enabled
        Tagging operational
        Optimum Switching Vectors:
          IP to MPLS Turbo Vector
          MPLS Turbo Vector
        Fast Switching Vectors:
          IP to MPLS Fast Switching Vector
          MPLS Turbo Vector
        MTU = 1550


I hope this helps.
Regards


--- Harry Reynolds <harry at juniper.net> wrote:

> I think I follow, but besides the option of ignoring
> an explicit mtu
> mismatch, which Juniper does not support, its seems
> you could also
> reconfigure the JNI's MTU so that it matches the
> cisco/rest of the
> subnet?
> 
> <<< default settings
> 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# run show interfaces fe-0/3/1 | match
> mtu 
>   Link-level type: Ethernet, MTU: 1514, Speed:
> 100mbps, Loopback:
> Disabled, Source filtering: Disabled,
>     Protocol inet, MTU: 1500
>     Protocol mpls, MTU: 1488
> 
> 
> << Smaller
> 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# set mtu 1400 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# commit 
> commit complete
> 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# run show interfaces fe-0/3/1 | match
> mtu    
>   Link-level type: Ethernet, MTU: 1400, Speed:
> 100mbps, Loopback:
> Disabled, Source filtering: Disabled,
>     Protocol inet, MTU: 1386
>     Protocol mpls, MTU: 1374
> 
> <<< Bigger
> 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# set mtu 1570 
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# commit 
> commit complete
> 
> [edit interfaces fe-0/3/1]
> harry at vpn06# run show interfaces fe-0/3/1 | match
> mtu    
>   Link-level type: Ethernet, MTU: 1570, Speed:
> 100mbps, Loopback:
> Disabled, Source filtering: Disabled,
>     Protocol inet, MTU: 1556
>     Protocol mpls, MTU: 1544
> 
> 
> 
> 
> 
> > -----Original Message-----
> > From: Hyunseog Ryu [mailto:r.hyunseog at ieee.org] 
> > Sent: Wednesday, July 19, 2006 2:04 PM
> > To: Harry Reynolds
> > Cc: juniper-nsp at puck.nether.net
> > Subject: Re: [j-nsp] OSPF MTU-IGNORE?
> > 
> > The Problem is that one of Cisco router doesn't
> allow user 
> > settable MTU from FastEthernet interface.
> > 
> > router(config-if)# mtu ?
> >    <64-42949672295> MTU size in bytes
> > 
> > router(config-if)# mtu 1520
> > % Interface FastEthernet1/1 does not support user
> settable mtu.
> > 
> > router(config-if)# ip mtu
> >   <68-1000000>  MTU (bytes)
> > 
> > router(config-if)# ip mtu 1520
> > % Invalid IP MTU specified; minimum 68, maximum
> 1500
> > 
> > Because of this one Cisco router, I couldn't use
> MPLS from 
> > this whole subnet.
> > I would like to replace this router, but I had no
> choice.
> > 
> > 
> > Another option was using "ip ospf mtu-ignore" from
> Cisco, but 
> > it seems 
> > that JUNOS doesn't support it.
> > 
> > So I think I'm in deadlock situation until I
> replaced those 
> > problematic 
> > Cisco router.
> > 
> > Hyun
> > 
> > 
> > Harry Reynolds wrote:
> > > The last I heard the answer was "no", in part
> because it 
> > breaks section
> > > 10.6. of the rfc.
> > > 
> > > Perhaps you can change the mtu on the JNI to
> match the cisco?
> > > 
> > > 
> > > Regards
> > > 
> > > 
> > >  
> > > 
> > >> -----Original Message-----
> > >> From: juniper-nsp-bounces at puck.nether.net 
> > >> [mailto:juniper-nsp-bounces at puck.nether.net] On
> Behalf Of 
> > Hyunseog Ryu
> > >> Sent: Wednesday, July 19, 2006 1:41 PM
> > >> To: juniper-nsp at puck.nether.net
> > >> Subject: [j-nsp] OSPF MTU-IGNORE?
> > >>
> > >>
> > >> Hi Guys,
> > >>
> > >> Currently I'm running Cisco/Juniper
> multi-vendor networks.
> > >> >From one of ethernet segment, I would like to
> change MTU for 
> > >> MPLS network.
> > >> But the problem is that one of cisco router
> doesn't allow to 
> > >> change MTU size for ehternet card.
> > >> So I would like to use "ip ospf mtu-ignore"
> command from Cisco.
> > >> I'm wondering whether Juniper has equivalent
> command or not.
> > >> This will disable OSPF MTU mismatch check for
> OSPF between routers.
> > >>
> > >> Thanks.
> > >>
> > >> Hyun
> > >>
> > >>
> > >> _______________________________________________
> > >> juniper-nsp mailing list
> juniper-nsp at puck.nether.net 
> > >>
> https://puck.nether.net/mailman/listinfo/juniper-nsp
> > >>
> > > 
> > > 
> > > 
> > 
> > 
> 
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
> 


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