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Help: source natting won't work on my CSM

robert.huang
Level 1
Level 1

Hi All,

My Cisco catalyst 6513 is connecting to another cisco 7513 router. Both of them have "network 0.0.0.0 0.0.0.0 area 0" in the OSPF statement so that all interfaces are inter-pingable. Real Servers "10.124.56.1" and "42.100.0.73" are loopback1 and loopback2 on the 7513 router. 42.108.128.1 is the Vlan 33 on the MSFC of the 6513 Switch.

6513_Ext1#sh run mod 5            
Building configuration...

Current configuration : 520 bytes
module ContentSwitchingModule 5
vlan 33 client
  ip address 42.108.128.2 255.255.255.0
  gateway 42.108.128.1
!
natpool POOL-TN3270 42.108.128.150 42.108.128.190 netmask 255.255.255.0
!
probe PROBE-PING icmp
!
serverfarm SF-TN3270
  nat server
  nat client POOL-TN3270
  predictor leastconns
  real 10.124.56.1
   inservice
  real 42.100.0.73
   inservice
  probe PROBE-PING
!
vserver VTN3270
  virtual 42.108.128.101 tcp 0
  serverfarm SF-TN3270
  persistent rebalance
  inservice
!
end

From my workstation 42.108.92.105, I start a telnet session to the VIP 42.108.128.101. But the session waits there and then times out. I can't see the login screen. From the below command, I can see the session is established. So I would think just the return traffic won't get back to my workstation. Please help me resolve this problem.  Thank you very much.


6513_Ext1#sh mod csm 5 conn detail

    prot vlan source                destination           state      
----------------------------------------------------------------------
In  TCP  33   42.108.92.105:2626    42.108.128.101:23     ESTAB      
Out TCP  33   42.100.0.73:23        42.108.128.150:8195   ESTAB      
    vs = VTN3270, ftp = No, csrp = False

6513_Ext1#

1 Reply 1

Gilles Dufour
Cisco Employee
Cisco Employee

I would suggest to take sniffer traces on the server and on the CSM portchannel.

Make sure the server does receive the SYN and check if the SYN/ACK comes back to the CSM.

Gilles.