[j-nsp] J6350 Jumbo frame MTU and OSPF setting

[Ben Dale]

Hi Harris

My apologies, I completely missed the fact that you were using fiber PIMs - maximum MTU for these is 9018 or 9014 if you have the multi-port version:

http://www.juniper.net/techpubs/software/junos-security/junos-security10.0/junos-security-swconfig-interfaces-and-routing/interfaces-physical-properties-section.html#interfaces-mtu-section

On 01/10/2010, at 8:36 PM, Harris Hui wrote:

> Hi Ben,
> 
> Looks like I can apply the MTU setting on the reth interface but cannot apply it on the fiber modules.
> 
> show interfaces reth4 
> Physical interface: reth4, Enabled, Physical link is Up
> Interface index: 132, SNMP ifIndex: 180
> Link-level type: Ethernet, MTU: 9192, Speed: 1000mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
> Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 0
> Device flags : Present Running
> Interface flags: SNMP-Traps Internal: 0x4000
> Current address: 00:10:db:ff:70:04, Hardware address: 00:10:db:ff:70:04
> Last flapped : 2010-10-01 10:24:25 UTC (00:03:48 ago)
> Input rate : 264 bps (0 pps)
> Output rate : 480 bps (0 pps)
> 
> Thanks
> Harris
> 
> <graycol.gif>Ben Dale ---10/01/2010 PM 02:11:40---Hi Harris
> 
> <ecblank.gif>
> From:	<ecblank.gif>
> Ben Dale <bdale at comlinx.com.au>
> <ecblank.gif>
> To:	<ecblank.gif>
> Harris Hui/Hong Kong/IBM at IBMHK
> <ecblank.gif>
> Cc:	<ecblank.gif>
> juniper-nsp at puck.nether.net
> <ecblank.gif>
> Date:	<ecblank.gif>
> 10/01/2010 PM 02:11
> <ecblank.gif>
> Subject:	<ecblank.gif>
> Re: [j-nsp] J6350 Jumbo frame MTU and OSPF setting
> 
> 
> 
> Hi Harris
> 
> On 01/10/2010, at 3:35 PM, Harris Hui wrote:
> 
> > I am trying to configure our J6350 fiber interface to MTU 9192 to get a
> > better TCP throughput. However, I can only able to configure the MTU size
> > below 1500, when I configure the MTU to 9192 and commit the changes, it
> > still shows MTU 1500 on the physical interface.
> 
> I've only got a 2320 in front of me right now, but your configuration below works fine (and the MTU changes) - what version of JUNOS are you running?
> 
> 
> > Do you have any experience on using Jumbo frame MTU size on the J6350? We
> > are also running OSPF across the private circuit, is JUNOS support "OSPF
> > ignore-mtu" like cisco?
> 
> No and we've been bitten by this before - I have raised an ER with my SE regarding this, but who knows how far away that will be.  You shouldn't need to use it if you control the routers on both ends (and the issue you are having with MTU goes away).
> 
> Cheers,
> 
> Ben
>