Remote SPAN traffic don't go over trunks

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Oct 22nd, 2009
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Hello everybody,

I would like to carry some traffic with a remote span vlan over trunks on some intermediate switches. Swithes are Catalyst 3560. But it don't work. The traffic enters through a trunk on the first intermediate switch but it stops there, it don't flow out of this switch through a second trunk?! Trunks are then connected to PtP WAN links...

Remote span vlan is created on the switch and allowed on trunks. VTP prunning is not enabled.


Any idea why traffic stops on the first intermediate switch?


Thanks in advance


Leo


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Giuseppe Larosa Thu, 10/22/2009 - 05:27
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Hello Leo,

you need to declare the remote span vlan as remote span also in intermediate switches.


see

Switch(config)# vlan 901


Switch(config-vlan)# remote span


Switch(config-vlan)# end



http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst3750/software/release/12.2_46_se/configuration/guide/swspan.html#wp1213360



this disables mac address learning and provides propagation of mirrored traffic


Hope to help

Giuseppe


Leo_Monten Thu, 10/22/2009 - 09:38
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Hello Giuseppe,

thanks for posting, but yes, I knew that, and RSPAN VLAN have been already declared as remote span, but nothing.

Traffic enters on the switch through one trunk, but is not forwarded out of it, through another trunk?!


BR

Leo

Giuseppe Larosa Thu, 10/22/2009 - 10:01
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Hello Leo,


check with

sh vlan id remote-span-vlan#


if other trunk ports permits the remote span vlan.


you may need to add the remote-span vlan in the list of permitted vlans on trunk to next switch.


if needed you need to add it on both sides of the trunk.


Hope to help

Giuseppe


Leo_Monten Fri, 10/23/2009 - 00:14
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Hi Giuseppe,

I've already done it but nothing. I made the whole config from source to destination port, including all trunks. RSPAN VLAN is shown that is present in all SW-es with command sh vlan remote-span. And is also enabled in all trunks. All other VLAN traffic flows ok.

The same problem appears every time, because I've tested this in more than one switch, through my WAN network, and every time was the same problem, traffic stops on the first intermediate switch.

But RSPAN works just fine when there is no need to carry SPAN traffic over intermediate switches. So, when the source and destination switches are only one hop far from.


So I've no idea what to try anymore, just to conclude that it DOESN'T WORK!


Anyhow, thank you for suggestions and posting


BR


Giuseppe Larosa Sat, 10/24/2009 - 04:24
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Hello Leo,

sorry you didn't solve this issue.

What type of switch is in the middle?


on cat3550 a reflector port was needed.


I've checked C3560 config guide but it is not required.


However, there are some restrictions about vlan-id used for RSPAN


The RSPAN VLAN cannot be VLAN 1 (the default VLAN) or VLAN IDs 1002 through 1005 (reserved for Token Ring and FDDI VLANs).


Hope to help

Giuseppe


Leo_Monten Mon, 10/26/2009 - 01:05
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Hello Giuseppe,

I've used normal range VLAN IDs for RSPAN. All switches are Catalyst 3560G, with IOS sw version 12.2(35)SE5.


I don't know what's the catch?!


Tnx for posts and help

BR

Leo

sawosankung Tue, 10/27/2009 - 14:22
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Hi Giuseppe


I am also experiencing this problem with C2950 switches. However, I noted that only one direction/way monitoring (ie SPAN source is either tx or rx but not both)is permitted where C2950 intermediary switches will be used.


But I would also like to know how reliable/stable SPAN/RSPAN is generally.


Thanks

sankung

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