topic Re: Cannot get second trunk working between 4506-E switches in Switching

Cannot get second trunk working between 4506-E switches

mhaught1964 — Wed, 06 Mar 2019 19:05:16 GMT

Hello All,

Would someone help me troubleshoot a trunking issue?

I am connecting two new 4506s (Sup 6-E in each with X2 converter modules) with SX SFPs over MMF at a distance of about 200 feet. Each switch has 2 SFPs, connected to ports Gi 1/3 and Gi 1/5

Both sides are configured like this:

interface GigabitEthernet1/3
switchport mode dynamic desirable
logging event link-status
logging event trunk-status
udld port aggressive
spanning-tree bpduguard disable

interface GigabitEthernet1/5
switchport mode dynamic desirable
logging event link-status
logging event trunk-status
udld port aggressive
spanning-tree bpduguard disable

When I issue the sh int trunk command, I get this output:

Port Mode Encapsulation Status Native vlan
Gi1/3 desirable 802.1q trunking 1

Port Vlans allowed on trunk
Gi1/3 1-4094

Port Vlans allowed and active in management domain
Gi1/3 1,142,217,802

Port Vlans in spanning tree forwarding state and not pruned
Gi1/3 1,142,217,802

As you can see, Gi 1/5 does not come up as a trunk. The switches are recognizing both SFPs, but I can't get the interface to come up on either switch

on interface Gi 1/5.

I've moved the working connection to other fiber strands, and my fiber is good. I also replaced SFPs and fiber patch cables.

Here's the output from sh interface on one of the "down" interfaces:

as912616s02#sh int gi 1/5

GigabitEthernet1/5 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet Port, address is 8843.e1b8.a084 (bia 8843.e1b8.a084)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, Auto-speed, link type is auto, media type is 1000Base SX

input flow-control is off, output flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 5d06h, output never, output hang never
Last clearing of "show interface" counters 00:00:07
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 input packets with dribble condition detected
     0 packets output, 0 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out

Nothing in the logs. Any idea what might be preventing the second fiber link from coming up? Any debug commands that may help? Any help is appreciated!

Thanks!

Mark

Re: Cannot get second trunk working between 4506-E switches

Federico Coto Fajardo — Thu, 13 May 2010 18:50:41 GMT

Mark,

The trunk through Gig1/3 works but not through Gig1/5

This is because the interface is down (or I'm missing something?)

as912616s02#sh int gi 1/5
GigabitEthernet1/5 is down, line protocol is down (notconnect)

Federico.

Re: Cannot get second trunk working between 4506-E switches

mhaught1964 — Thu, 13 May 2010 18:57:29 GMT

Thanks for your response.

Yes, I know the interface is down, but the SFPs, patch cables and fiber are good, so it should have come up like Gi 1/3.

If I move the working fiber from Gi 1/3 to Gi 1/5 on both switches, the trunk comes up on Gi 1/5. What could be keeping the two switches from allowing a second trunk to come up? I know spanning tree will block it as park it as a redundant path, but that shouldn't prevent the interface from showing up/up.

Re: Cannot get second trunk working between 4506-E switches

Federico Coto Fajardo — Thu, 13 May 2010 18:59:50 GMT

But the interface shows as down (not connected)... as not detecting anything on that interface.

If you move the non-working fiber that you have on Gig1/5 to Gig1/3 comes up?

Federico.

Re: Cannot get second trunk working between 4506-E switches

mhaught1964 — Thu, 13 May 2010 19:07:58 GMT

Yes, all the fiber is working and all the SFPs are working. If I take the working trunk (Gi 1/3 to Gi 1/3) and move both sides to Gi 1/5, the trunk comes up again on Gi 1/5. So, it doesn't appear to be a fiber, SFP or patch cable issue. The Sup just won't let more than one SFP come up at a time.

Re: Cannot get second trunk working between 4506-E switches

Federico Coto Fajardo — Thu, 13 May 2010 19:10:05 GMT

The SFP only allows one trunk?

If you have the trunk working on Gig1/5 and you connect the other one to Gig1/3 (Gig1/3 shows down and not coming up)?

Federico.