black listing of web traffic

Andrey Gordon andrey.gordon at gmail.com
Tue Feb 9 16:44:01 CST 2010


Thanks to all,
The problem seems to be fixed by changing the NAT ip to something else and
than back.

It does seem much like NAT exhaustion even though the f/w claims only 13K
session for two dynamic NATs and about 20 static ones.
What I don't get is why there is consistency in opening sites. Why does
facebook open all the time and store.apple.com barely opens all the time.
I'd say if it would be NAT exhaustion, they would all behave the same way
meaning open and then not open and then open again.

It is solved for the time being.
Again, thanks to all.

-----
Andrey Gordon [andrey.gordon at gmail.com]


On Tue, Feb 9, 2010 at 5:34 PM, Andrey Gordon <andrey.gordon at gmail.com>wrote:

> I don't know, that's true. I don't where to find that info in this
> particular firewall would be a more correct statement. and my f/w guy is not
> much help either.
> It definitely looks to me like a NATting issue, but what I don't understand
> is why the same sites (e.g. facebook) loads fine consistently and others
> don't. NAT exhaustion would not allow that, imo.
>
> This is the only relevant info I was able to find in the box:
>
> andrey.gordon at PA-2050-Bos> show session info
>
>
>
> -------------------------------------------------------------------------------
> number of sessions supported:                   262143
> number of active sessions:                      6799
> number of active TCP sessions:                  5906
> number of active UDP sessions:                  889
> number of active ICMP sessions:                 4
> number of active BCAST sessions:                0
> number of active MCAST sessions:                0
> number of predict sessions:                     1884
> session table utilization:                      2%
> number of sessions created since system bootup: 142823265
> Packet rate:                                    5920/s
> Throughput:                                     45871 Kbps
>
> -------------------------------------------------------------------------------
>
>
>
>
> -----
> Andrey Gordon [andrey.gordon at gmail.com]
>
>
> On Tue, Feb 9, 2010 at 5:31 PM, Nathan Ward <nward at daork.net> wrote:
>
>> You don't know how many NAT sessions are open though, right?
>>
>> This is where I'd start looking, if you do or not is up to you.
>>
>> On 10/02/2010, at 11:26 AM, Andrey Gordon wrote:
>>
>> Well, if I understand NATting right, I should be able to have at least
>> 65000 sessions per NAT address to one destination. Am I wrong? the firewall
>> is rated for 260K sessions.
>>
>> -----
>> Andrey Gordon [andrey.gordon at gmail.com]
>>
>>
>> On Tue, Feb 9, 2010 at 5:22 PM, Nathan Ward <nward at daork.net> wrote:
>>
>>> 13,000 sessions could be your problem - perhaps you are running out of
>>> NAT state table space.
>>>
>>> On 10/02/2010, at 11:18 AM, Andrey Gordon wrote:
>>>
>>> Not 100% sure. I have more than one NAT address on that firewall two of
>>> which are dynamic: student and business. It's the student one that's broken.
>>> Now, with that said, the Palo Alto firewall shows 13,000 session in
>>> progress. Even the f/w guy does not know how to check out the session count
>>> per NATted IP.
>>>
>>> -----
>>> Andrey Gordon [andrey.gordon at gmail.com]
>>>
>>>
>>> On Tue, Feb 9, 2010 at 5:08 PM, Nathan Ward <nward at daork.net> wrote:
>>>
>>>> How many users do you have behind your NAT?
>>>>
>>>> On 10/02/2010, at 11:04 AM, Andrey Gordon wrote:
>>>>
>>>> > Thx to all the folks replying off the list.
>>>> >
>>>> > The more I trouble shoot the more I'm convinced that it's not the
>>>> sites that
>>>> > are doing rate-limiting. I went to a website of one of my previous
>>>> employers
>>>> > (a small company). Chances of them having a fancy reverse proxy with
>>>> some
>>>> > sort of black list filtering are slim to none, yet their site barely
>>>> opens
>>>> > up as well.
>>>> >
>>>> > Must be something that either my firewall device is doing (which is
>>>> what is
>>>> > doing the NATting) or I don't' know what else. I'm working with my
>>>> firewall
>>>> > guy since f/w is his domain and I have no clue about that vendor of
>>>> the
>>>> > firewalls (PaloAlto).
>>>> >
>>>> > Thanks all for the suggestions. I'll keep digging.
>>>> >
>>>> > -----
>>>> > Andrey Gordon [andrey.gordon at gmail.com]
>>>> >
>>>> >
>>>> > On Tue, Feb 9, 2010 at 4:56 PM, Jay Hennigan <jay at west.net> wrote:
>>>> >
>>>> >> Andrey Gordon wrote:
>>>> >>
>>>> >>> Can't find my IP on any of the black lists. Don't have any proxies.
>>>> Sites
>>>> >>> that behave poorly are consistent. That is to say that facebook.com
>>>> ,
>>>> >>> apple.com would always come up without an issue, but cnn.com,
>>>> >>> forever21.com(i know, don't ask, students),
>>>> >>> store.apple.com would consistently take forever to come up.
>>>> >>>
>>>> >>> Just wanted to check of rate-limiting web clients is a common
>>>> practice
>>>> >>> nowdays in the industry. If it's not, it's probably an unlikely
>>>> cause of
>>>> >>> my
>>>> >>> troubles...
>>>> >>>
>>>> >>
>>>> >> It could be that the problem sites have some form of load balancer
>>>> that has
>>>> >> an issue keeping state on multiple sessions from the same IP.
>>>> >>
>>>> >> You mentioned that changing the source IP fixed it.  Is this a
>>>> temporary
>>>> >> fix that breaks after several users access the sites from the new IP?
>>>> >>
>>>> >> --
>>>> >> Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
>>>> >> Impulse Internet Service  -  http://www.impulse.net/
>>>> >> Your local telephone and internet company - 805 884-6323 - WB6RDV
>>>> >>
>>>> >
>>>> >
>>>> >
>>>> >
>>>>
>>>>
>>>
>>>
>> !DSPAM:22,4b71e13583451376319610!
>>
>>
>>
>



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