isa server 2004 (proxy chain loop)

Posted on 2009-04-22
Last Modified: 2012-06-21
Event Type:      Warning
Event Source:      Microsoft ISA Server Web Proxy
Event Category:      None
Event ID:      14141

I've installed isa server with 2 NIC

the 1 NIC
no gateway

the 2 NIC

IPv4 Route Table
Interface List
0x1 ........................... MS TCP Loopback interface
0x10003 ...00 0e 2e 71 c4 7f ...... Realtek RTL8139 Family PCI Fast Ethernet NIC

0x10004 ...00 0f 1f de 27 ba ...... Broadcom NetXtreme 57xx Gigabit Controller
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
     20      1     10     20     10     20     10     20     10     20      1      1
Default Gateway:

i get these errors:

Date:            22.4.2009
Time:            10:39:36
User:            N/A
Computer:      my server
ISA Server detected a proxy chain loop. There is a problem with the configuration of the ISA Server routing policy.

Question by:RodeRidder
    LVL 10

    Expert Comment

    both of your NICs are on the same subnet, so there is effectively two routes to any traffic on the same subnet - it can go out on one card and back in on the other.
    You need to change the interface to be on another subnet, either by changing its IP address to something outside of the subnet or reduce the size of the subnet significantly.... very significantly.
    What are you actually trying to achieve here, as it may be more relevant to fix that issue rather then the one listed

    Author Comment

    NIC 1 is on my internal network
    NIC 2 is connected to my cisco pix router

    i would like my clients to connect to the outside(internet) and my VPN clients to connect to the inside
    LVL 10

    Accepted Solution

    Change the NIC connected to the CISCO to be on a subnet of Give that a default gateway of the Cisco INTERNAL interface (which will also need to be changed)
    I suggest the following config:
    Internal NIC:, no gateway,
    External NIC:, gateway of,
    Cisco: internal NIC, External NIC of whatever it has now
    That should get you routing correctly
    LVL 10

    Expert Comment

    Oh, and subnet masks all round of

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