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List Info
Thread: comcast routing issue question
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| comcast routing issue question |
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2006-11-30 05:06:29 |
Question: What could cause the first trace below to
succeed, but the
second trace to fail?
$ mtr 69.61.40.35
HOST: blue Loss% Snt Last Avg
Best Wrst
1. 192.168.3.1 0.0% 1 4.3 4.3
4.3 4.3
2. 73.62.48.1 0.0% 1 10.6 10.6
10.6 10.6
3. 68.86.108.25 0.0% 1 11.4 11.4
11.4 11.4
4. 68.86.106.54 0.0% 1 9.8 9.8
9.8 9.8
5. 68.86.106.9 0.0% 1 20.5 20.5
20.5 20.5
6. 68.86.90.121 0.0% 1 11.3 11.3
11.3 11.3
7. 68.86.84.70 0.0% 1 27.7 27.7
27.7 27.7
8. 64.213.76.77 0.0% 1 24.5 24.5
24.5 24.5
9. 208.50.254.150 0.0% 1 39.4 39.4
39.4 39.4
10. 208.49.83.237 0.0% 1 46.6 46.6
46.6 46.6
11. 208.49.83.234 0.0% 1 40.7 40.7
40.7 40.7
12. 69.61.40.35 0.0% 1 43.9 43.9
43.9 43.9
$ mtr 69.61.40.34
HOST: blue Loss% Snt Last Avg
Best Wrst
1. 192.168.3.1 0.0% 1 1.1 1.1
1.1 1.1
2. 73.62.48.1 0.0% 1 9.9 9.9
9.9 9.9
3. 68.86.108.25 0.0% 1 9.3 9.3
9.3 9.3
4. 68.86.106.54 0.0% 1 9.6 9.6
9.6 9.6
5. 68.86.106.9 0.0% 1 9.0 9.0
9.0 9.0
6. 68.86.90.121 0.0% 1 18.2 18.2
18.2 18.2
7. 68.86.84.70 0.0% 1 23.9 23.9
23.9 23.9
8. ??? 100.0 1 0.0 0.0
0.0 0.0
Taking the 69.61.40.33/28 subnet a bit further, .36 drops at
68.86.84.70
but .37 - .39 make it. .40 drops at 68.86.84.70, but .41
makes it.
Crazy.
-Jim P.
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| comcast routing issue question |
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2006-11-30 05:28:30 |
On Thu, 2006-11-30 at 00:06 -0500, Jim Popovitch wrote:
> Question: What could cause the first trace below to
succeed, but the
> second trace to fail?
>
> $ mtr 69.61.40.35
> HOST: blue Loss% Snt Last
Avg Best Wrst
> 1. 192.168.3.1 0.0% 1 4.3
4.3 4.3 4.3
> 2. 73.62.48.1 0.0% 1 10.6
10.6 10.6 10.6
> 3. 68.86.108.25 0.0% 1 11.4
11.4 11.4 11.4
> 4. 68.86.106.54 0.0% 1 9.8
9.8 9.8 9.8
> 5. 68.86.106.9 0.0% 1 20.5
20.5 20.5 20.5
> 6. 68.86.90.121 0.0% 1 11.3
11.3 11.3 11.3
> 7. 68.86.84.70 0.0% 1 27.7
27.7 27.7 27.7
> 8. 64.213.76.77 0.0% 1 24.5
24.5 24.5 24.5
> 9. 208.50.254.150 0.0% 1 39.4
39.4 39.4 39.4
> 10. 208.49.83.237 0.0% 1 46.6
46.6 46.6 46.6
> 11. 208.49.83.234 0.0% 1 40.7
40.7 40.7 40.7
> 12. 69.61.40.35 0.0% 1 43.9
43.9 43.9 43.9
>
> $ mtr 69.61.40.34
> HOST: blue Loss% Snt Last
Avg Best Wrst
> 1. 192.168.3.1 0.0% 1 1.1
1.1 1.1 1.1
> 2. 73.62.48.1 0.0% 1 9.9
9.9 9.9 9.9
> 3. 68.86.108.25 0.0% 1 9.3
9.3 9.3 9.3
> 4. 68.86.106.54 0.0% 1 9.6
9.6 9.6 9.6
> 5. 68.86.106.9 0.0% 1 9.0
9.0 9.0 9.0
> 6. 68.86.90.121 0.0% 1 18.2
18.2 18.2 18.2
> 7. 68.86.84.70 0.0% 1 23.9
23.9 23.9 23.9
> 8. ??? 100.0 1 0.0
0.0 0.0 0.0
>
>
> Taking the 69.61.40.33/28 subnet a bit further, .36
drops at 68.86.84.70
> but .37 - .39 make it. .40 drops at 68.86.84.70, but
.41 makes it.
>
> Crazy.
Btw, the problem has now been resolved, however I'm still
curious as to
what scenario could have caused that.
-Jim P.
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| comcast routing issue question |
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2006-11-30 06:23:41 |
On Thu, Nov 30, 2006 at 12:28:30AM -0500, Jim Popovitch
wrote:
>
> On Thu, 2006-11-30 at 00:06 -0500, Jim Popovitch wrote:
> > Question: What could cause the first trace below
to succeed, but the
> > second trace to fail?
> >
[snip]
> > Taking the 69.61.40.33/28 subnet a bit further,
.36 drops at 68.86.84.70
> > but .37 - .39 make it. .40 drops at 68.86.84.70,
but .41 makes it.
> >
> > Crazy.
>
> Btw, the problem has now been resolved, however I'm
still curious as to
> what scenario could have caused that.
Perhaps CEF-style load balancing over multiple paths, with
one of them
down and not properly failing over? Per-flow balancing
would decide
which path to use based on source & target IP.
> -Jim P.
>
--
Jordan.
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| comcast routing issue question |
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2006-11-30 06:59:50 |
On Thu, Nov 30, 2006 at 12:06:29AM -0500, Jim Popovitch
wrote:
> $ mtr 69.61.40.34
> HOST: blue Loss% Snt Last
Avg Best Wrst
> 1. 192.168.3.1 0.0% 1 1.1
1.1 1.1 1.1
> 2. 73.62.48.1 0.0% 1 9.9
9.9 9.9 9.9
> 3. 68.86.108.25 0.0% 1 9.3
9.3 9.3 9.3
> 4. 68.86.106.54 0.0% 1 9.6
9.6 9.6 9.6
> 5. 68.86.106.9 0.0% 1 9.0
9.0 9.0 9.0
> 6. 68.86.90.121 0.0% 1 18.2
18.2 18.2 18.2
> 7. 68.86.84.70 0.0% 1 23.9
23.9 23.9 23.9
> 8. ??? 100.0 1 0.0
0.0 0.0 0.0
>
>
> Taking the 69.61.40.33/28 subnet a bit further, .36
drops at 68.86.84.70
> but .37 - .39 make it. .40 drops at 68.86.84.70, but
.41 makes it.
You're not the only one who noticed this.
http://www.dsl
reports.com/forum/remark,17368208
--
| Jeremy Chadwick jdc at
parodius.com |
| Parodius Networking http://www.parodius.com/
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| UNIX Systems Administrator Mountain
View, CA, USA |
| Making life hard for others since 1977. PGP:
4BD6C0CB |
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| comcast routing issue question |
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2006-11-30 07:20:11 |
On Wed, Nov 29, 2006, Jeremy Chadwick wrote:
> >
> > Taking the 69.61.40.33/28 subnet a bit further,
.36 drops at 68.86.84.70
> > but .37 - .39 make it. .40 drops at 68.86.84.70,
but .41 makes it.
>
> You're not the only one who noticed this.
Not that its probably it; but i've seen some crappy
etherchannel links
with IP path selection exhibit this whacky behaviour.
Adrian
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| comcast routing issue question |
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2006-11-30 20:09:54 |
On 11/29/06, Jim Popovitch <jimpop yahoo.com> wrote:
> On Thu, 2006-11-30 at 00:06 -0500, Jim Popovitch wrote:
> > Question: What could cause the first trace below
to succeed, but the
> > second trace to fail?
> >
> > $ mtr 69.61.40.35
> > HOST: blue Loss% Snt
Last Avg Best Wrst
> > 1. 192.168.3.1 0.0% 1
4.3 4.3 4.3 4.3
> > 2. 73.62.48.1 0.0% 1
10.6 10.6 10.6 10.6
> > 3. 68.86.108.25 0.0% 1
11.4 11.4 11.4 11.4
> > 4. 68.86.106.54 0.0% 1
9.8 9.8 9.8 9.8
> > 5. 68.86.106.9 0.0% 1
20.5 20.5 20.5 20.5
> > 6. 68.86.90.121 0.0% 1
11.3 11.3 11.3 11.3
> > 7. 68.86.84.70 0.0% 1
27.7 27.7 27.7 27.7
> > 8. 64.213.76.77 0.0% 1
24.5 24.5 24.5 24.5
> > 9. 208.50.254.150 0.0% 1
39.4 39.4 39.4 39.4
> > 10. 208.49.83.237 0.0% 1
46.6 46.6 46.6 46.6
> > 11. 208.49.83.234 0.0% 1
40.7 40.7 40.7 40.7
> > 12. 69.61.40.35 0.0% 1
43.9 43.9 43.9 43.9
> >
> > $ mtr 69.61.40.34
> > HOST: blue Loss% Snt
Last Avg Best Wrst
> > 1. 192.168.3.1 0.0% 1
1.1 1.1 1.1 1.1
> > 2. 73.62.48.1 0.0% 1
9.9 9.9 9.9 9.9
> > 3. 68.86.108.25 0.0% 1
9.3 9.3 9.3 9.3
> > 4. 68.86.106.54 0.0% 1
9.6 9.6 9.6 9.6
> > 5. 68.86.106.9 0.0% 1
9.0 9.0 9.0 9.0
> > 6. 68.86.90.121 0.0% 1
18.2 18.2 18.2 18.2
> > 7. 68.86.84.70 0.0% 1
23.9 23.9 23.9 23.9
> > 8. ??? 100.0 1
0.0 0.0 0.0 0.0
> >
> >
> > Taking the 69.61.40.33/28 subnet a bit further,
.36 drops at 68.86.84.70
> > but .37 - .39 make it. .40 drops at 68.86.84.70,
but .41 makes it.
> >
> > Crazy.
>
> Btw, the problem has now been resolved, however I'm
still curious as to
> what scenario could have caused that.
>
> -Jim P.
eBGP multihop peering across a pair of 10 gigE links with
static routes pointing to the remote router loopback; one
link goes south, but the interface still shows as up/up,
and voila, depending upon the hash, your packets may
go across the good link, or they may disappear into the
black hole of oblivion.
This is why multipath is a good thing, and eBGP multihop
with static routes is a Bad Thing(tm).
Matt
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