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Multiple PIX with Access-list

Posted on 2006-06-28
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Last Modified: 2010-08-05
Hi Guys,

Here is the scenario


                              DMZ                        Private
Internet--------PIX1------------------PIX2----------
all the hosts on DMZ have the PIX2 As gateway
PIX1 will allow access to Internet from DMZ
PIX2 has Deny any any on DMZ internface
PIX2 has route as follows
0000 0000 PIX1 gateway.
Now a host on DMZ wants to access Internet, Do i need to allow access on PIX2

The host traffic will hit the PIX2 DMZ interface then the default route will direct to PIX1.
to do this does the PIX2 need to have the access-rule????? or will it forward it without accessrule??
However there is a default deny any any on DMZ interface of PIX2

regards
Naren
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Question by:r_naren22atyahoo
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LVL 79

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by:lrmoore
ID: 17008103
You have to change the default gateway to PIX1
PIX2 will not redirect the traffic regardless of acls or rules.
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LVL 79

Expert Comment

by:lrmoore
ID: 17008116
As long as you are natting between PIX2 and the DMZ there are no other routes needed on the hosts.
If you are not natting between them and all nat is on PIX1, then you need an additional route statement on the dmz hosts for the private lan IP pointing to PIX2
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by:r_naren22atyahoo
ID: 17008216
Why?

If the Hosts on DMZ has PIX2 intf as the gateway.

then

the dmz hosts traffic comes to PIX2,
 if the traffice is fors private then it will direct to private, then if the traffic is for internet then
the default route on PIX2 i.e. 0000 0000 any to DMZ1 Intf of PIX1
will direct to PIX1 interface rite???

what exactly is wrong in the above scenario???
anyway the NAT is only on PIX1
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lrmoore earned 125 total points
ID: 17008299
What's wrong is the basic design principles of the pix. It will not redirect any packet out the same interface it arrived on. It will proccess it through to another interface without problem. A router would "bounce" it to the designated gateway in its route table. A PIX is not a router and does not behave the same way. A router will also send an icmp redirect to the host saying "that route is at gateway xxxx" and this creates a dynamic route table on the host so that next packets go directly to the alternate gateway. Pix will not send this redirect packet either.

With NAT only on PIX1 then you will have to add static route entries on the hosts for lan subnet behind pix2 and default gateway to pix1


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LVL 11

Expert Comment

by:prueconsulting
ID: 17012902
Throw a layer 3 switch or router in the DMZ and allow it to make your routing descions and direct accordingly if you want to have those machines point to a single GW.  Point them at the switch
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