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New Member

Juniper SSG 20 multimode fiber interface with Cisco 4506 switch


Here's the problem.

There's one Juniper SSG 20 firewall with JX-SFP-1GE-SX multimode fiber interface (850nm) (which I can control) and I have to connect it to Cisco 4506 switch which has WS-X4306-GB module and WS-G5484 GBIC interface (also multimode fiber).

SSG 20 shows link up. Cisco shows link down.

Unfortunatelly I don't have Cisco 4506 to play with, but I have to find solution for this system. Cisco 4506 show version is:

#show version

Cisco IOS Software, Catalyst 4000 L3 Switch Software (cat4000-I9K91S-M), Version 12.2(25)EWA9, RELEASE SOFTWARE (fc3) Technical Support: Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 21-Mar-07 12:20 by tinhuang Image text-base: 0x10000000, data-base: 0x115C6158

ROM: 12.2(31r)SGA1

Dagobah Revision 226, Swamp Revision 34

XXXXXXX uptime is 3 weeks, 1 day, 3 hours, 20 minutes System returned to ROM by reload System restarted at 13:19:45 CEST Mon May 19 2008 System image file is "bootflash:cat4000-i9k91s-mz.122-25.EWA9.bin"

I was able to replicate issue with Cisco 3524 swtich (SSG20 shows link up, Cisco link down, physical down), and solution that I found was to enter interface level command: (config-if)#no negotiation auto. After this command, everything was showing state as "UP" and working as expected (there was traffic going through the optic)

When I suggested this command as a solution, administrator from the other side was claiming that this command returns "invalid input detected at ^ marker".

Can anyone tell me is there any known issue between those two products, and maybe alternative to this command, so I can turn off this IEEE 802.3z negotiation if that's the problem.

Thanks for assistance



  • LAN Switching and Routing

Re: Juniper SSG 20 multimode fiber interface with Cisco 4506 swi


I had faced exactly the same problem when connecting a multimode from cisco 7600 to alcatel 1850. But the same thing " no neg" worked for me.

If the admin on the other side is not familiar with the router can you ask him to just execute " no neg" rather than "no neg auto" I remember using just "no negotiation" The command was a bit diff on 7600. just give it a try.



New Member

Re: Juniper SSG 20 multimode fiber interface with Cisco 4506 swi

So I found my solution, but I want to know why is like this.

So the solution was to enter on Cisco following command (config-if)#speed nonegotiate

From this link:

I can see on section: Configuring Link Negotiation on Gigabit Ethernet Ports that this command is doing negotiation exchange of flow-control parameters, remote fault information, and duplex information. Link negotiation is enabled by default.

And the funniest thing of all is, this speed nonegotiate command doesn't deal with the speed at all :)

Can someone confirm me what are remote fault information and flow control parameters

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