[Xorp-users] XORP IGMPv2 <-> XORP IGMPv3
Philip Romanov
philip_romanov at yahoo.com
Thu Oct 8 10:03:29 PDT 2009
Hello,
I'm researching how XORP IGMP implementation behaves when it comes to v3/v2/v1 co-existence on the same network.
I have IGMPv3 RFC3376 in front of me:
7.3. Multicast Router Behavior
7.3.1. In the Presence of Older Version Queriers
IGMPv3 routers may be placed on a network where at least one router
on the network has not yet been upgraded to IGMPv3. The following
requirements apply:
o If any older versions of IGMP are present on routers, the querier
MUST use the lowest version of IGMP present on the network. This
must be administratively assured; routers that desire to be
compatible with IGMPv1 and IGMPv2 MUST have a configuration option
to act in IGMPv1 or IGMPv2 compatibility modes. When in IGMPv1
mode, routers MUST send Periodic Queries with a Max Resp Code of 0
and truncated at the Group Address field (i.e., 8 bytes long), and
MUST ignore Leave Group messages. They SHOULD also warn about
receiving an IGMPv2 or IGMPv3 query, although such warnings MUST be
rate-limited. When in IGMPv2 mode, routers MUST send Periodic
Queries truncated at the Group Address field (i.e., 8 bytes long),
and SHOULD also warn about receiving an IGMPv3 query (such warnings
MUST be rate-limited). They also MUST fill in the Max Resp Time in
the Max Resp Code field, i.e., the exponential algorithm described
in section 4.1.1 is not used.
o If a router is not explicitly configured to use IGMPv1 or IGMPv2
and hears an IGMPv1 Query or IGMPv2 General Query, it SHOULD log a
warning. These warnings MUST be rate-limited.
I placed two XORP routers on two PCs (connection is point-to-point), with relevant part of IGMP configuration being:
XORP-1:
igmp {
interface eth1 {
vif eth1 {
disable: false
version: 3
}
}
traceoptions {
flag all {
disable: false
}
}
}
XORP-2:
igmp {
interface eth1 {
vif eth1 {
disable: false
version: 2
}
}
traceoptions {
flag all {
disable: false
}
}
}
I'm watching for IGMP protocol exchanges from one of the PCs with wireshark. I see that XORP-1 continues to send IGMPv3 queries while XORP-2 continues to send IGMPv2 queries. Furthermore, XORP-1 replies itself to queries using v3 and XORP-2 using v2 so I have a great mix of V2 and V3 request/response traffic on my network. It does not appear that XORP-1 downshifted into IGMPv2 compatibility mode.
Question, I guess, would be if XORP supports downshifting into lower version IGMP compatibility modes as per RFC? Any configuration file options that I missed?
I can provide pcap capture if needed.
Regards,
Philip Romanov
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