UDP 5440 not connecting between two Lan-to-Lan VPN's on a Cisco VPN 3000

Posted on 2008-10-15
Last Modified: 2012-05-05
I have a WAN with three locations.  HQ, Dallas, and Boston.  There is a VPN 3005 in HQ the connects the two other locations.  Dallas has a ASA and Boston has a PIX, both connected using IPSec back to HQ.

I also have a VOIP system in all three locations.  HQ can connect to both remote locations, but the VOIP system in Dallas cannot connect to the VOIP system in Boston.  It uses UDP 5440.  The two remote offices can ping eachother and other TCP communication works.

As far as I can tell, I have no filters or access control lists that would be blocking this.  Any ideas?
Question by:davidmccarthy
LVL 10

Expert Comment

ID: 22726816
If TCP works and UDP does not it has to be a ACL issue...

Have a look at the configs and see if there's something like a::

  access-list permit 101 tcp (...)

but no:

  access-list permit 101 udp (....)

If so, change it to:

  access-list permit 101 ip (...)

That'll allow TCP + UDP.

Maybe post your configs if you still can't figure it out?
Be sure to remove all usernames/passwords first!

Author Comment

ID: 22726912
kyleb84: I don't think that's my problem.  Here's more detail:

HQ is
Dallas is
Boston is

In the Boston PIX, the tunnel is setup with:

access-list TunnelToHQ permit ip
access-list TunnelToHQ permit ip

Likewise the Dallas ASA has:

object-group network HQ
access-list outside_20_cryptomap extended permit ip object-group HQ
access-list inside_nat0_outbound extended permit ip object-group HQ

I'm leaving out a bunch of stuff here, but it's because I don't think it is relevant.  The UDP traffic I'm having trouble with flows fine between both remote offices and HQ.  

I think the problem must be some combination of the VPN 3005 in HQ and/or the core router in HQ.

There are no access-list at all on the core router (  It has the following routing table: <internet firewall> <connected>  <vpn 3005> <vpn 3005>

It might be impossible to list all of the configuration of the VPN3005 since it is mostly web-based, but neither Lan-to-Lan tunnel has a filter on it.  The tunnel default gateway is

When I traceroute from Dallas to Boston (because ICMP does work), it goes to the Dallas ASA -> Core Router -> VPN 3005 > Boston

As far as I know routing is the same for TCP and UDP, but maybe my routing scheme is affecting the UDP packets?

LVL 10

Expert Comment

ID: 22726956
""As far as I know routing is the same for TCP and UDP, but maybe my routing scheme is affecting the UDP packets?""

I don't see how... routing only happens at layer 3 - IP, not layer 4 - TCP/UDP.

What you've described is exactly how it should be set up, and your ICMP pings proves that the routing is properly configured.


You say it's the VoIP system that need to communicate via UDP... I'm guessing your tests were made on a PC?

How is the routing table set up on those VoIP systems?

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Author Comment

ID: 22733884
I'm using Shoretel VOIP switches.  Here's the routing table from Boston:

destination      gateway
-------------      -----------   is the PIX in Boston and is the VOIP box.

When I telnet into VOIP box I can run a standard ping to the Dallas VOIP just fine.  When I run what Shoretel calls a "lsp_ping", it fails.  According to their tech support, the lsp_ping is trying to communicate using UDP 5440.  So of course, they are claiming that something must be blocking it along way.

I suppose another approach would be to eliminate the VOIP all together and prove that I can get UDP 5440 from one location to the other.  I know how to test TCP stuff, like telneting to a specific port on a server to see if it connects.  How can I simulate something like that with UDP?

LVL 10

Accepted Solution

kyleb84 earned 500 total points
ID: 22736304
There's a little app called iperf. It's really for bandwidth testing but does UDP + TCP.

There's a Microsoft Windows Binary about half way down that page.

install on your laptop and a server at the other site.

Server @ Site1:
iperf -s -u

Your laptop:
iperf -c [IP OF SERVER 1] -u

If it works you'll see something similar to what I've attached.

U:\>iperf -s -u
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 8.00 KByte (default)
[1928] local port 5001 connected with port 1322
[ ID] Interval       Transfer     Bandwidth       Jitter   Lost/Total Datagrams
[1928]  0.0-10.0 sec  1.25 MBytes  1.05 Mbits/sec  0.000 ms    0/  893 (0%)
U:\>iperf -c -u
Client connecting to, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 8.00 KByte (default)
[1912] local port 1322 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[1912]  0.0-10.0 sec  1.25 MBytes  1.05 Mbits/sec
[1912] Server Report:
[1912]  0.0-10.0 sec  1.25 MBytes  1.05 Mbits/sec  0.000 ms    0/  893 (0%)
[1912] Sent 893 datagrams
If it didn't work, you'll only see this on the server:
U:\>iperf -s -u
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 8.00 KByte (default)

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LVL 10

Expert Comment

ID: 22736315
Well I guess it wouldn't be your laptop, since you'd be at HQ, but anyway, you get the point.

Expert Comment

ID: 24828186
Dude.  I'm having this issue and it's driving me mad!

How did you fix it?

Expert Comment

ID: 36509669
But, where is teh answer?

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