Router SLB configuration problem, fast responses appreciated

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Feb 28th, 2010
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Hi folks,

I am trying to understand why my SLB configuration isn't working, and would really appreciate some advice on this.

I'm using dispatched mode, as the web servers are locally connected to the router via a switch.  Here's a simple summary of my configuration.

interface GigabitEthernet0/0/0

ip address

description Internet


interface GigabitEthernet0/0/1

ip address

description Internal


ip slb serverfarm FARM







ip slb vserver VIP

virtual tcp www

serverfarm FARM


r1#sh ip slb reals

real                  farm name        weight  state          conns

-------------------------------------------------------------------       FARM             8       OPERATIONAL    0       FARM             8       OPERATIONAL    0     

r1#sh ip slb vservers

slb vserver      prot  virtual                  state         conns    interface(s)


VIP             TCP     OPERATIONAL   0        <any>

So everything seems to look OK - but when I telnet to port 80 of the virtual server, I get connection refused.

Please would someone advise me on how to debug this, and what could be going wrong?



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philipplant Sun, 02/28/2010 - 14:15
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Well this was on an ASR1002, running asr1000rp1-advipservicesk9.  I thought maybe there was a software glitch so I updated the code to asr1000rp1-advipservicesk9.

However the later version doesn't even support SLB, so maybe there was an issue there.  Oh well.  Goodbye SLB, hello temporary rotary NAT (shudder).


Gilles Dufour Mon, 03/01/2010 - 02:15
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  • Cisco Employee,

For the future, the way to debug this is to capture a sniffer trace and see if the SYN came to the router, and if it was forwarded to the server.

Then, you need to check where the server sent the SYN/ACK.

If it bypasses the router, we can't reverse nat server -> vip and the client gets a SYN/ACK from an unknown ip address.



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