Question

Allowing Port 25 on Cisco 857 ADSL router

Asked by: matthew_129

Hi
Ive got my Cisco 857 connected to my Sonicwall's WAN port. I have Mailmarshal setup in the DMZ on a server, but I cant get the Cisco to let in any port 25 requests. port 25 between the cisco and the DMZ is fine and useable.

-Cisco Internal IP 10.0.0.1
-Sonicwall WAN IP 10.0.0.10
-Sonicwall DMZ IP 172.16.0.10
-Mailmarshal IP 172.16.0.1

I can telnet from the cisco to mailmarshal on port 25. I just cant get from the outside of the cisco.

Can someone please take a look at my cisco config as below and see where ive gone wrong with it

IRISHORTR1#show run
Building configuration...
 
Current configuration : 5151 bytes
!
version 12.4
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug uptime
service timestamps log uptime
service password-encryption
service sequence-numbers
no service dhcp
!
hostname IRISHORTR1
!
boot-start-marker
boot-end-marker
!
logging buffered 10240
logging console critical
enable password 7 13061E010803
!
no aaa new-model
clock timezone NZST 12
clock summer-time NZDT recurring 1 Sun Oct 2:00 3 Sun Mar 3:00
!
!
dot11 syslog
no ip source-route
!
!
ip cef
ip inspect name firewall tcp
ip inspect name firewall udp
ip inspect name firewall cuseeme
ip inspect name firewall h323
ip inspect name firewall rcmd
ip inspect name firewall realaudio
ip inspect name firewall streamworks
ip inspect name firewall vdolive
ip inspect name firewall sqlnet
ip inspect name firewall tftp
ip inspect name firewall ftp
ip inspect name firewall icmp
ip inspect name firewall sip
ip inspect name firewall esmtp max-data 52428800
ip inspect name firewall fragment maximum 256 timeout 1
ip inspect name firewall rtsp
ip inspect name firewall pptp
no ip bootp server
no ip domain lookup
ip domain name Iris.local
!
!
!
file verify auto
!
!
archive
 log config
  hidekeys
 path flash:config
 write-memory
!
!
ip tcp selective-ack
ip tcp timestamp
!
!
!
interface ATM0
 no ip address
 no atm ilmi-keepalive
 dsl operating-mode auto
!
interface ATM0.1 point-to-point
 pvc 0/100
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface Vlan1
 ip address 10.0.0.1 255.255.255.0
 ip access-group 102 in
 ip nat inside
 ip virtual-reassembly
!
interface Dialer0
 ip address negotiated
 ip access-group 101 in
 no ip redirects
 no ip unreachables
 ip inspect firewall out
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 dialer pool 1
 dialer-group 1
 no cdp enable
 ppp pap sent-username username@xtra.co.nz password 7 11111111111111111111111
 ppp ipcp dns request
 ppp ipcp route default
!
ip forward-protocol nd
ip route 172.16.0.0 255.255.255.0 10.0.0.10
!
no ip http server
no ip http secure-server
ip nat inside source list 1 interface Dialer0 overload
ip nat inside source static tcp 172.16.0.1 25 interface Dialer0 25
ip nat inside source static tcp 10.0.0.10 80 interface Dialer0 80
ip nat inside source static tcp 10.0.0.10 443 interface Dialer0 443
ip nat inside source static tcp 172.16.0.1 3389 interface Dialer0 3389
!
access-list 1 remark The local LAN.
access-list 1 permit 10.0.0.0 0.0.0.255
access-list 1 permit 172.16.0.0 0.0.0.255
access-list 2 remark Where management can be done from.
access-list 2 permit 10.0.0.0 0.0.0.255
access-list 101 remark Traffic allowed to enter the router from the Internet
access-list 101 deny   ip 0.0.0.0 0.255.255.255 any
access-list 101 deny   ip 10.0.0.0 0.255.255.255 any
access-list 101 deny   ip 127.0.0.0 0.255.255.255 any
access-list 101 deny   ip 169.254.0.0 0.0.255.255 any
access-list 101 deny   ip 172.16.0.0 0.15.255.255 any
access-list 101 deny   ip 192.0.2.0 0.0.0.255 any
access-list 101 deny   ip 192.168.0.0 0.0.255.255 any
access-list 101 deny   ip 198.18.0.0 0.1.255.255 any
access-list 101 deny   ip 224.0.0.0 0.15.255.255 any
access-list 101 deny   ip any host 255.255.255.255
access-list 101 permit tcp any any eq 1723
access-list 101 permit gre any any
access-list 101 deny   icmp any any echo
access-list 101 permit tcp any any eq 443
access-list 101 permit tcp any any eq smtp
access-list 101 permit tcp any any eq www
access-list 101 permit tcp any any eq 3389
access-list 101 permit ip any any log
access-list 101 permit ip 172.16.0.0 0.15.255.255 any
access-list 102 remark Traffic allowed to enter the router from the Ethernet
access-list 102 permit ip any host 10.0.0.1
access-list 102 deny   ip any host 10.0.0.255
access-list 102 deny   udp any any eq tftp log
access-list 102 deny   ip any 0.0.0.0 0.255.255.255 log
access-list 102 deny   ip any 127.0.0.0 0.255.255.255 log
access-list 102 deny   ip any 169.254.0.0 0.0.255.255 log
access-list 102 deny   ip any 192.0.2.0 0.0.0.255 log
access-list 102 deny   ip any 192.168.0.0 0.0.255.255 log
access-list 102 deny   ip any 198.18.0.0 0.1.255.255 log
access-list 102 deny   udp any any eq 135 log
access-list 102 deny   tcp any any eq 135 log
access-list 102 deny   udp any any eq netbios-ns log
access-list 102 deny   udp any any eq netbios-dgm log
access-list 102 deny   tcp any any eq 445 log
access-list 102 permit ip 10.0.0.0 0.0.0.255 any
access-list 102 permit ip any host 255.255.255.255
access-list 102 permit ip any any log
dialer-list 1 protocol ip permit
!
control-plane
!
banner motd ^C
Original config prepared by administrator@mydomain.com
 
You require authorisation to connect to this device.
If you are not authorised to connect to this device please disconnect now.  If
you fail to disconnect you may be prosecuted under the Crimes Amendment
Act 2003 section 252 under New Zealand law.
 
^C
!
line con 0
 no modem enable
line aux 0
line vty 0 4
 access-class 2 in
 password 7 045802150C2E
 login
!
scheduler max-task-time 5000
end

                                  
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Asked On
2009-08-20 at 17:07:42ID24670002
Tags

Cisco

,

Telnet

,

SMTP

Topics

Network Routers

,

DSL Lines / Cable Internet

,

Simple Mail Transfer Protocol (SMTP)

Participating Experts
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Comments
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Answers

 

by: wiscomPosted on 2009-08-20 at 17:47:48ID: 25148297

Hi,

Static NAT port forwarding will only perform at directly connected networks. So in this case to the 10.0.0.x network.

The only solution to portforward from the Internet to network address 172.16.0.1 is to portforward twise:

on the router it will be:

ip nat inside source static tcp 10.0.0.10 25 interface Dialer0 25

on the firewall it will be

ip nat inside source static tcp 172.16.0.1 25 10.0.0.10 25

of course you need to configure the firewall with a default gatway address pointed to address 10.0.0.1 and on the server to 172.16.0.10

Add also this acl statement:

access-list 101 permit tcp any any eq 25

Finally, replace this acl statement:

access-list 102 permit ip any host 10.0.0.1

ino

access-list 102 permit ip any host 10.0.0.10

To do this follow these tesps:

no access-list 102
access-list 102 remark Traffic allowed to enter the router from the Ethernet
access-list 102 permit ip any host 10.0.0.10
access-list 102 deny   ip any host 10.0.0.255
access-list 102 deny   udp any any eq tftp log
access-list 102 deny   ip any 0.0.0.0 0.255.255.255 log
access-list 102 deny   ip any 127.0.0.0 0.255.255.255 log
access-list 102 deny   ip any 169.254.0.0 0.0.255.255 log
access-list 102 deny   ip any 192.0.2.0 0.0.0.255 log
access-list 102 deny   ip any 192.168.0.0 0.0.255.255 log
access-list 102 deny   ip any 198.18.0.0 0.1.255.255 log
access-list 102 deny   udp any any eq 135 log
access-list 102 deny   tcp any any eq 135 log
access-list 102 deny   udp any any eq netbios-ns log
access-list 102 deny   udp any any eq netbios-dgm log
access-list 102 deny   tcp any any eq 445 log
access-list 102 permit ip 10.0.0.0 0.0.0.255 any
access-list 102 permit ip any host 255.255.255.255
access-list 102 permit ip any any log
end


NOTE: please perform all this from the CONSOLE interface of the router and the firewall !!!!!!

Good luck !


A/

 

by: mikecrPosted on 2009-08-20 at 21:18:15ID: 25149119

That's not entirely true. You can NAT backward into your network to an IP address that is not directly connected as long is it's not natted on the next device in line and there is a route to get to it.

Mathew, let's rule out security as a problem and remove the access lists from the VLAN interface and the Dialer interface and then try to telnet again and let's see what happens. The NAT is correct but the access lists are pretty restrictive so let's rule them out as a possible cause.

 

by: matthew_129Posted on 2009-08-20 at 21:40:33ID: 25149184

Actually...

It appears that the particular ISP in use at this site blocks all port 25 traffic in an attempt to reduce spam being routed through thier customers. I have applied to be exempt from the port 25 blocking, so should hopefully see it work in the next few hours/days.

All the port 25 traffic just stops at or before the router, none of my tools could determine where it stops, where as RDP on port 3385 happily sails on through to the server its pointed at.

I will post back with a responce when i determine if the ISP unblocking port 25 works or not, Thanks all the same for the input so far

 

by: matthew_129Posted on 2009-08-21 at 13:42:38ID: 25155628

Ok,

It was deffinatly the ISP blocking port 25, Ive just had confirmation from them that its now unblocked and I can now happily use that port

Thanks for the input

 

by: mikecrPosted on 2009-08-21 at 14:49:29ID: 25156164

Good job!

20120131-EE-VQP-002

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