Hello everyone
I was looking around and noticed a pretty bad route from DTAG to Tata
AS6453 (basically destination was Tata Comm's Indian network on AS4755). I
am not able to understand cause for inefficient routing but I am sure I am
failing to understand something which is crazy in their IGP. The result is
that route from Europe to India is via Europe > US > Singapore > India
rather then direct India.
There seem to be quite a few prefixes with these problem, but for this mail
question, I am picking two prefixes - one which seems to be having good
routing.
202.54.82.0/24 has pretty bad routing while 93.183.28.0/24. I see both
prefixes have valid route objects and are originated by VSNL AS4755 to Tata
AS6453 in India. Now if we compare trace from Tata's own core router say in
Paris from their looking glass, I get:
Router: gin-pye-core1
Site: FR, Paris, PYE
Command: traceroute ip 202.54.82.1
Tracing the route to RAS55.1.ppppun.vsnl.net.in (202.54.82.1)
1 if-1-0-0-2.tcore1.PYE-Paris.as6453.net (80.231.154.45) [MPLS: Label
525297 Exp 0] 300 msec
if-0-0-0-0.tcore1.PYE-Paris.as6453.net (80.231.154.37) [MPLS: Label
525297 Exp 0] 260 msec
if-1-0-0-2.tcore1.PYE-Paris.as6453.net (80.231.154.45) [MPLS: Label
525297 Exp 0] 260 msec
2 if-5-2.tcore1.L78-London.as6453.net (80.231.130.1) [MPLS: Label 523604
Exp 0] 264 msec
if-3-6.tcore1.L78-London.as6453.net (80.231.130.85) [MPLS: Label 523604
Exp 0] 256 msec
if-5-2.tcore1.L78-London.as6453.net (80.231.130.1) [MPLS: Label 523604
Exp 0] 264 msec
3 if-2-2.tcore2.L78-London.as6453.net (80.231.131.1) [MPLS: Label 728466
Exp 0] 264 msec
* if-1-2.tcore2.L78-London.as6453.net
<http://if-1-2.tcore2.L78-London.as6453.net> (80.231.130.122) [MPLS: Label
728466 Exp 0] 264 msec 268 msec*
* 4 if-20-2.tcore2.NYY-NewYork.as6453.net
<http://if-20-2.tcore2.NYY-NewYork.as6453.net> (216.6.99.13) [MPLS: Label
354225 Exp 0] 276 msec 260 msec 260 msec*
5 *
if-12-6.tcore1.CT8-Chicago.as6453.net (216.6.99.46) [MPLS: Label 365409
Exp 0] 304 msec
if-11-2.tcore1.NYY-NewYork.as6453.net (216.6.99.2) [MPLS: Label 782881
Exp 0] 256 msec
6 if-22-2.tcore2.CT8-Chicago.as6453.net (64.86.79.1) [MPLS: Label 361921
Exp 0] 264 msec 264 msec
if-1-2.tcore1.PDI-PaloAlto.as6453.net (66.198.127.5) [MPLS: Label
670352 Exp 0] 256 msec
7 if-11-3.tcore2.PDI-PaloAlto.as6453.net (66.198.144.57) [MPLS: Label
321233 Exp 0] 256 msec
if-2-2.tcore2.PDI-PaloAlto.as6453.net (66.198.127.2) [MPLS: Label
321233 Exp 0] 260 msec *
8 if-9-2.tcore1.TV2-Tokyo.as6453.net (180.87.180.18) 280 msec 260 msec
260 msec
9 if-2-2.tcore2.TV2-Tokyo.as6453.net (180.87.180.2) [MPLS: Label 581761
Exp 0] 252 msec 252 msec 252 msec
10 if-6-2.tcore1.SVW-Singapore.as6453.net (180.87.12.109) [MPLS: Label
710034 Exp 0] 248 msec 244 msec 248 msec
11 if-5-2.tcore1.CXR-Chennai.as6453.net (180.87.12.54) 244 msec 272 msec
252 msec
12 180.87.36.10 272 msec 256 msec 272 msec
13 172.31.19.94 272 msec 252 msec 256 msec
14 * *
172.25.83.142 288 msec
15 172.25.83.134 !H * *
while for other prefix, route is:
Router: gin-pye-core1
Site: FR, Paris, PYE
Command: traceroute ip 93.183.28.1
Tracing the route to 93.183.28.1
1 if-1-0-0-2.tcore1.PYE-Paris.as6453.net (80.231.154.45) [MPLS: Label
519713 Exp 0] 12 msec
if-0-0-0-0.tcore1.PYE-Paris.as6453.net (80.231.154.37) [MPLS: Label
519713 Exp 0] 12 msec
if-1-0-0-2.tcore1.PYE-Paris.as6453.net (80.231.154.45) [MPLS: Label
519713 Exp 0] 12 msec
2 if-8-1600.tcore1.WYN-Marseille.as6453.net (80.231.217.5) [MPLS: Label
302880 Exp 0] 12 msec
if-14-2.tcore1.WYN-Marseille.as6453.net (80.231.154.170) [MPLS: Label
302880 Exp 0] 36 msec
if-8-1600.tcore1.WYN-Marseille.as6453.net (80.231.217.5) [MPLS: Label
302880 Exp 0] 12 msec
*3 if-2-2.tcore2.WYN-Marseille.as6453.net
<http://if-2-2.tcore2.WYN-Marseille.as6453.net> (80.231.217.2) 12 msec 12
msec 12 msec*
4 80.231.200.26 140 msec 116 msec 116 msec
5 172.31.16.193 148 msec 140 msec 144 msec
* 6 115.114.71.133.static-chennai.vsnl.net.in
<http://115.114.71.133.static-chennai.vsnl.net.in> (115.114.71.133) [AS
4755] 140 msec 148 msec 140 msec*
7 172.29.209.82 [MPLS: Labels 301664/7167 Exp 1] 148 msec 144 msec 148
msec
8 172.31.35.138 [MPLS: Labels 4831/7167 Exp 1] 152 msec 152 msec 148 msec
9 121.242.126.205.static-chennai.vsnl.net.in (121.242.126.205) [AS 4755]
[MPLS: Label 7167 Exp 1] 148 msec * 140 msec
10 121.242.126.206.static-chennai.vsnl.net.in (121.242.126.206) [AS 4755]
140 msec 148 msec 140 msec
11 * * *
12 * * *
Now if I focus on best route entry in router for both prefixes, I see
following:
Bad Prefix:
4755
tv2-tcore1. (metric 16148) from *hk2-core3.* (hk2-core3.)
Origin IGP, valid, internal, best
Community:
Originator: 66.110.10.113
Good Prefix:
4755
wyn-tcore2. (metric 10050) *from wyn-tcore2.* (66.110.10.109)
Origin IGP, valid, internal, best
Community:
Now as I understand Paris router is getting bad prefix from TV2 which is
their Tokyo router while for other prefix with good routing, route is via
their other router on cable landing station in France.
Can someone explain me what exactly is happening here? Are they missing
some iBGP sessions? It's not perfect mesh & missing route reflectors?
Probably both prefixes are originated inside India by different routers but
as I understand all prefixes get transit from AS6453 and so is it like
AS6453 missing some routes (which seem to be direct) to technically
downstream AS4755?
Curious to hear your thoughts.
Note: I am not worried about issue - it's not really impacting me. Just
trying to learn what is wrong in the backbone design here.
Thanks.