[mpls-linux-general] ldp_linux problem

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Hi,

I tried ldp_linux on my testbed with 3 routers (2 LERs + 1 LSR) but I got
a problem with the LSR.

Topology:
(networks 10.0.a.0 with netmask 255.255.255.0 for each subnet 10.0.a.0)

Host1 eth1---eth1 LERA eth2---eth2 LSR eth3---eth3 LERB eth4---eth4 Host2
       1.1    1.2       2.1    2.2      3.1    3.2       4.1    4.2

The problem is that there is no label swapping at the LSR on packets from
LER B to LER A. The LSR swaps labels correctly for packets from LER A to
LER B:

(ping from LER A to LER B with route recording on)
$ ping -R -c1 10.0.4.2
PING 10.0.4.2 (10.0.4.2) from 10.0.1.1 : 56(124) bytes of data.
64 bytes from 10.0.4.2: icmp_seq=0 ttl=253 time=0.5 ms
RR:     10.0.1.1
        10.0.2.1
        10.0.3.1   --> due to no label swapping by the LSR
        10.0.4.1
        10.0.4.2
        10.0.4.2
        10.0.3.2   --> 10.0.2.2 is absent (expected)
        10.0.1.2
        10.0.1.1

contents of /proc/net/mpls_*:
* on LER A

LABELSPACE:
eth2    0

FEC:
40004804 10.0.3.0/24
40004c04 10.0.4.0/24

TUNNEL:

IN:
40004000 gen 16 0 POP DLV
40004400 gen 17 0 POP DLV
40004800 gen 18 0 POP DLV
40004c00 gen 19 0 POP DLV
40005000 gen 20 0 POP DLV

OUT:
40004804 PUSH(gen 18) SET(eth2)
40004c04 PUSH(gen 19) SET(eth2)

* on LSR

LABELSPACE:
eth2    0
eth3    0

FEC:
40004404 10.0.1.0/24
40004805 10.0.4.0/24

TUNNEL:

IN:
40004000 gen 16 0 POP DLV
40004400 gen 17 0 POP DLV
40004800 gen 18 0 POP DLV
40004c00 gen 19 0 POP DLV
40005000 gen 20 0 POP DLV
40005400 gen 21 0 POP DLV
40005800 gen 22 0 POP DLV
40005c00 gen 23 0 POP FWD(40004404)
40006000 gen 24 0 POP DLV
40006400 gen 25 0 POP DLV
40006800 gen 26 0 POP DLV
40006c00 gen 27 0 POP DLV

OUT:
40004404 PUSH(gen 17) SET(eth2)
40004805 PUSH(gen 18) SET(eth3)

* On LER B

LABELSPACE:
eth3    0

FEC:
40005c05 10.0.1.0/24
40006005 10.0.2.0/24

TUNNEL:

IN:
40004000 gen 16 0 POP DLV
40004400 gen 17 0 POP DLV
40004800 gen 18 0 POP DLV
40004c00 gen 19 0 POP DLV
40005000 gen 20 0 POP DLV

OUT:
40005c05 PUSH(gen 23) SET(eth3)
40006005 PUSH(gen 24) SET(eth3)

Routing tables (only the information about subnets 10.0.x.0 is relevant):
LER A
$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Iface
10.0.4.0        10.0.2.2        255.255.255.0   UG    0      eth2
10.0.1.0        *               255.255.255.0   U     0      eth1
10.0.2.0        *               255.255.255.0   U     0      eth2
10.0.3.0        10.0.2.2        255.255.255.0   UG    0      eth2

LSR
$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Iface
10.0.4.0        10.0.3.2        255.255.255.0   UG    0      eth3
10.0.1.0        10.0.2.1        255.255.255.0   UG    0      eth2
10.0.2.0        *               255.255.255.0   U     0      eth2
10.0.3.0        *               255.255.255.0   U     0      eth3

LER B
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Iface
10.0.4.0        *               255.255.255.0   U     0      eth4
10.0.1.0        10.0.3.1        255.255.255.0   UG    0      eth3
10.0.2.0        10.0.3.1        255.255.255.0   UG    0      eth3
10.0.3.0        *               255.255.255.0   U     0      eth3

The routing tables are symetric, but the label bindings are not !
Do you have an explication about this behavior ? why is an entry in the
LSR label forwarding table missing ?

Thanks,

 Yvan Pointurier
________________________________________________________________________
 yv...@po...                             University of Virginia
 http://www.pointurier.org               Department of Computer Science