Commit bffd5ebe authored by Robert Ricci's avatar Robert Ricci

Added notes on porting switchmac, previously sent to Keith Sklower @

Berkeley in email.
parent 3ca16939
......@@ -240,3 +240,29 @@ not possible to do through SNMP something we'd been doing for years.
You can, of course, try out the OIDs we use in snmpit_cisco and snmpit_intel -
some of them may be supported on your switch.
#####
##### switchmac
#####
wwitchmac is a script, used at installation time, to print out all the MAC
adresses a switch has learned, and what ports they're on. The idea is to
eliminate the need for the testbed administrators to manually enter which nodes
are connected to which ports on which switches.
The stuff in this should be pretty standard - ie. this script has support for
Intel, Nortel, and Cisco switches, and I suspect that one of these should work
pretty similarly to whatever switch you're trying to port it to.
In your switch vendor's documentation, take a look for the dot1dTpFdbTable in
the BRIDGE-MIB (which is a standard one.)
The main ickiness in this script is something called 'Community String
Indexing' - see, the MIB is designed for switches that store one MAC table that
is VLAN-independant (ie. you can't use the same MAC in two different VLANs at
once.) Cisco keeps a MAC table per-VLAN. So, the way they get around this is to
change the community string you use to get access to the MAC table for each
VLAN. So, if your community string is 'public', and you want to look at the
MAC table for VLAN 42, you talk to the switch with the community string
'public@42'. Terrible. I don't know if other switch vendors use this same hack,
or if they will have some other hack of their own.
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