Introduction
In this sample configuration, a PIX Firewall is configured in order to allow the traversal of two different Voice over IP (VoIP) protocols—H.323, and Session Initiation Protocol (SIP). Due to the fact that VoIP protocols are made up of signaling and IP address/port combinations, there are a number of issues with VoIP and Network Address Translations (NAT). The PIX Firewall fixup protocol addresses these issues.
Prerequisites
Requirements
There are no specific requirements for this document.
Components Used
The information in this document is based on these software and hardware versions:
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PIX Software Release 6.3.1
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Cisco 2651XM IOS® 12.3(3)
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Cisco Analog Telephone Adaptor (ATA) 186 version 2.16.1
Note: For PIX Firewall (with VoIP application-layer gateway [ALG] or fixup protocol), these version/feature combinations are supported:
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Version 5.2—Supports H.323 version 2, Registration and Status (RAS), and NAT (no PAT)
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Version 6.0 and 6.1—Adds SIP with NAT (no PAT), Skinny Client Control Protocol (SCCP) with NAT (no PAT), and no Media Gateway Control Protocol (MGCP) support
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Version 6.2—PAT support for H.323 version 2 and SIP.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Conventions
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: Use the Command Lookup Tool ( registered customers only) to obtain more information on the commands used in this section.
Network Diagram
This document uses this network setup:
Configurations
This document uses these configurations:
| Cisco PIX Firewall |
|---|
PIX Version 6.3(1) |
| Cisco 2651 |
|---|
version 12.3 |
Verify
Use this section to confirm that your configuration works properly.
The Output Interpreter Tool ( registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
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show xlate—Displays the translation that takes place.
pixfirewall#show xlate
1 in use, 1 most used
Global 100.1.1.5 Local 192.168.0.2
!--- Translation in place
Verify H.323
Use these commands in order to verify the H.323:
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show call active voice brief—Displays the contents of the active call table. The information presented includes call times, dial peers, connections, quality of service parameters, and gateway handling of jitter.
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show h225—Displays calls that go through the PIX Firewall.
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show conn detail—Displays the NAT of both the VoIP signaling and media addresses.
This is the output of the show call active voice brief command.
Gateway#show call active voice brief
Telephony call-legs: 1
SIP call-legs: 0
H323 call-legs: 1
MGCP call-legs: 0
Multicast call-legs: 0
Total call-legs: 2
2828 : 1574769hs.1 +142 pid:1111 Answer 1111 active
dur 00:00:06 tx:159/24803 rx:343/54880
IP 100.1.1.5:16384 rtt:0ms pl:3860/0ms lost:0/1/0 delay:64/64/65ms g711ulaw
2828 : 1574770hs.1 +141 pid:2222 Originate 2222 active
dur 00:00:06 tx:343/54880 rx:167/26083
Tele 1/0/0 (48): tx:8200/3290/0ms g711ulaw noise:-50 acom:13 i/0:-42/-55 dBm
This is the output of the show h225 command.
pixfirewall#show h225
Total H.323 Calls: 1
1 Concurrent Call(s) for
Local: 192.168.0.2/16230 Foreign: 100.1.1.2/1720
1. CRV 5735
Local: 192.168.0.2/16230 Foreign: 100.1.1.2/1720
!--- This output indicates that there is currently one active
!--- H.323 call going through the PIX Firewall between the local
!--- endpoint 192.168.0.2 and foreign host 100.1.1.2. For these
!--- particular endpoints, there is one concurrent call between them,
!--- with a Call Reference Value (CRV) for that call of 5735.
This is the output of the show conn detail command.
pixfirewall#show conn detail
7 in use, 12 most used
Flags: A - awaiting inside ACK to SYN, a - awaiting outside ACK to SYN,
B - initial SYN from outside, C - CTIQBE media, D - DNS, d - dump,
E - outside back connection, F - outside FIN, f - inside FIN,
G - group, g - MGCP, H - H.323, h - H.225.0, I - inbound data, i - incomplete,
k - Skinny media, M - SMTP data, m - SIP media, O - outbound data,
P - inside back connection, q - SQL*Net data, R - outside acknowledged FIN,
R - UDP RPC, r - inside acknowledged FIN, S - awaiting inside SYN,
s - awaiting outside SYN, T - SIP, t - SIP transient, U - up
UDP outside:100.1.1.2/17047 inside:192.168.0.2/16385 flags H
UDP outside:100.1.1.2/17046 inside:192.168.0.2/16384 flags H
TCP outside:100.1.1.2/1720 inside:192.168.0.2/14785 flags UIOh
UDP outside:100.1.1.2/0 inside:192.168.0.2/16384 flags Hi
TCP outside:100.1.1.2/11012 inside:192.168.0.2/14793 flags UIO
TCP outside:100.1.1.2/11012 inside:192.168.0.2/0 flags sSiaA
TCP outside:100.1.1.2/11012 inside:192.168.0.2/0 flags sSiaA
Verify the SIP
Use these commands in order to verify the SIP.
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show call active voice brief—Displays the contents of the active call table. The information presented includes call times, dial peers, connections, quality of service parameters, and gateway handling of jitter.
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show conn detail—Displays the NAT of both the VoIP signaling and media addresses.
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show sip—Displays an active SIP call.
This is the output of the show call active voice brief command.
Gateway#show call active voice brief
Telephony call-legs: 1
SIP call-legs: 1
H323 call-legs: 0
MGCP call-legs: 0
Multicast call-legs: 0
Total call-legs: 2
1210 : 1589226hs.1 +133 pid:1111 Answer 1111 active
dur 00:00:13 tx:344/53687 rx:639/102001
IP 100.1.1.5:16384 rtt:0ms pl:11420/0ms lost:0/1/0 delay:45/45/65ms g711ulaw
1210 : 1589227hs.1 +132 pid:2222 Originate 2222 active
dur 00:00:13 tx:639/102001 rx:344/53687
Tele 1/0/0 (50): tx:14760/6780/0ms g711ulaw noise:-49 acom:13 i/0:-45/-50 dBm
This is the output of the show sip command.
pixfirewall#show sip
Total: 1
call-id 648032863@192.168.0.2
state Active, idle 0:00:58
This is the output of the show conn detail command.
pixfirewall#show conn detail
7 in use, 12 most used
Flags: A - awaiting inside ACK to SYN, a - awaiting outside ACK to SYN,
B - initial SYN from outside, C - CTIQBE media, D - DNS, d - dump,
E - outside back connection, F - outside FIN, f - inside FIN,
G - group, g - MGCP, H - H.323, h - H.225.0, I - inbound data, i - incomplete,
k - Skinny media, M - SMTP data, m - SIP media, O - outbound data,
P - inside back connection, q - SQL*Net data, R - outside acknowledged FIN,
R - UDP RPC, r - inside acknowledged FIN, S - awaiting inside SYN,
s - awaiting outside SYN, T - SIP, t - SIP transient, U - up
UDP outside:100.1.1.2/5060 inside:192.168.0.2/0 flags ti
UDP outside:100.1.1.2/0 inside:192.168.0.2/5060 flags Tti
UDP outside:100.1.1.2/0 inside:192.168.0.2/16384 flags mi
UDP outside:100.1.1.2/5060 inside:192.168.0.2/5060 flags Tt
UDP outside:100.1.1.2/17490 inside:192.168.0.2/16384 flags m
UDP outside:100.1.1.2/17491 inside:192.168.0.2/0 flags m
UDP outside:100.1.1.2/17490 inside:192.168.0.2/0 flags mi
Troubleshoot
Troubleshooting Commands
The Output Interpreter Tool ( registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
Note: Refer to Important Information on Debug Commands before you use debug commands.
Use these debug commands to troubleshoot the PIX.
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debug sip—Displays the SIP messages generated from the gateways.
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debug h323 h225 asn1—Displays the H.225 message generated from the gateways.
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debug—Displays the traffic that is encrypted.
Use these debug commands in order to troubleshoot the Cisco IOS gateway.
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debug voip ccapi inout—Displays the call setup and teardown operations performed on both the telephony and network call legs.
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debug h225 asn1—Displays the ASN.1 contents of any H.225 message sent or received.