Spanning tree

[glio]

I'm using NW5.1 + sp7. The SLP screws very often... clients can't log in because of SLP... and many advise me to turn off "spanning tree" and see if it makes a difference. We have a 3Com 4924 as the core and three 4400s for all the workstations. I turned off Spanning tree for all the 4400s and 4924 and all hell let loose: IP conflict... workstations couldn't ping one another and the whole network's dead.

After turning on the spanning tree on the 4924, everything returned to normal.

What the heck is this spanning tree??? Why turning this off can help SLP?

Jimmy

 

[techr]

Please tell me how many NICs do you have in your server?

 

[Papa4]

Cisco web site has a good definition of "spanning tree"

Spanning-Tree Protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly, only one active path can exist between two stations.

Multiple active paths between stations cause loops in the network. If a loop exists in the network topology, the potential exists for duplication of messages. When loops occur, some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded.

To provide path redundancy, Spanning-Tree Protocol defines a tree that spans all switches in an extended network. Spanning-Tree Protocol forces certain redundant data paths into a standby (blocked) state. If one network segment in the Spanning-Tree Protocol becomes unreachable, or if Spanning-Tree Protocol costs change, the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path.

Spanning-Tree Protocol operation is transparent to end stations, which are unaware whether they are connected to a single LAN segment or a switched LAN of multiple segments.

 

[MickEVH]

I had problems with spanning tree (STP) a while ago - the Spanning tree infrastructure was recalculating itself avery few seconds and chweing up all the bandwidth.

The advice to me from 3com was to disable STP on the edge switches (we have 4050 core, 49XX 2nd tier & 4400 at edges.)

As detailed in previous post, STP is there to protect you N/W from going nuts if there are multiple paths between end stations or "loops" in the network infrastructure. A better course of action is to track down the redundent links are get rid of them so that you have star or bus topology. There are better way to provide resilience between switch - LACP is my favourite.

Mick

 

[TimRegester]

SLP or Service Location Protocol is a multicast technology meaning that it is sent out by a server to all PCs and other devices on the network that are listening. In the IP only form of netware, without the IPX/SPX protocol previous versions used, it advertises that the server is there and allows the client to login.

I have seen issues with Novell and switched networks primarily because the network is not set up to work with multicast technologies specifically it cannot route multicast traffic accross VLANs. I have tried using IGMP and DVMRP as well as PIM for multicast routing accross VLANS to no avail, this is known to 3Com see knowledgebase article 3KB551 for more detail.

The best solution is to set up a preferred server on each client and maybe use an LMhosts or hosts file on the client PC, it is not elegant and can be an admin nightmare but it works. You can also create "scopes" in NDS to better manage this issue. Check the Novell website there was a good paper on all this.

Multicast may have seemed a good idea in principle but was no real replacement for SAPs which you could troubleshoot easily without resorting to a protocol analyser.

As for Spanning Tree, it would affect multicast as well as unicast and broadcast traffic in the same way, but if the muticast traffic reaches all the ports it needs to via the open physical paths it would not in any way explain why SLP is misbehaving.

As for turning off STP on the edge ports, this can make sense if you have pretty good confidence that some bozo will not be plugging a switch or hub into two ports simultaneously