Hello All,
Our main internet connection went down today and I realised that I really should have a backup plan in place to handle inbound email. Luckily I had a Cisco 877 knocking around doing not much. The mail server (Microsoft Exchange) has two network connections, one to the internet with a public IP and one to our internal network with a private IP. The default route is set to the ISP's gateway.
I set up the 877 with a DSL connection using SDM (I know, but it's quick) and used NAT to forward port 25 to the internal IP address of the mailserver. Obviously the mailserver does not route the traffic back to the 877 but tries to send it through the ISP's gateway.
The question is: How can I get NAT to translate the source address of the incoming mail to the 877's local IP address?
I seem to remember that Microsoft ISA Server had a tick box on the firewall rules called something like 'Requests appear to come from the ISA server computer'. That's basically what I'm trying to do.
Any ideas?
Thanks,
Chris
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version 12.4
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hostname rrir04
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clock summer-time PCTime date Mar 30 2003 1:00 Oct 26 2003 2:00
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crypto pki trustpoint TP-self-signed-1401562236
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description $ES_WAN$$FW_OUTSIDE$
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interface FastEthernet0
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interface FastEthernet1
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interface FastEthernet2
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interface FastEthernet3
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interface Vlan1
description $ETH-SW-LAUNCH$$INTF-INFO-HWIC 4ESW$$ES_LAN$$FW_INSIDE$
ip address 172.16.7.252 255.255.248.0
ip nat inside
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ip tcp adjust-mss 1452
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interface Dialer0
ip address negotiated
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ppp chap password 7 xxxx
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ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 Dialer0
ip route 192.168.16.0 255.255.255.0 172.16.7.254
ip http server
ip http authentication local
ip http secure-server
ip http timeout-policy idle 60 life 86400 requests 10000
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ip nat inside source list 1 interface Dialer0 overload
ip nat inside source static tcp 172.16.0.2 25 interface Dialer0 25
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access-list 1 remark INSIDE_IF=Vlan1
access-list 1 remark CCP_ACL Category=2
access-list 1 permit 172.16.0.0 0.0.7.255
dialer-list 1 protocol ip permit
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