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New Member

Problems with DHCP relay on PIX


I have a problem with DHCP relay agent on pix configured for simple PAT (Lab envirement)

All works fine with client ip statically configured:


DHCPRelay(config)# sh conn

1 in use, 4 most used

TCP out in idle 0:00:02 Bytes 91 flags UIO

DHCPRelay(config)# sh xlate

1 in use, 5 most used

PAT Global Local


BUT as soon as I change the client ip assignment to dynamic, absolutely nothing happens event with a <debug dhcprelay event> on the pix.

A sniffer shows only broadcast DHCPDISCOVER from the client and no reaction from the PIX.

The PIX DHCR relay is configured as needed, I don?t know why it?s not responding to DHCPDISCOVER, by the way it?s the same behaviour with STATIC / NAT configured!

Any idea?

Think you in advance!

Here is the PIX configuration:

PIX Version 6.3(4)

interface ethernet0 auto

interface ethernet1 100full

nameif ethernet0 outside security0

nameif ethernet1 inside security100

enable password xxx

passwd xxx

hostname DHCPRelay


fixup protocol dns maximum-length 512

fixup protocol ftp 21

fixup protocol h323 h225 1720

fixup protocol h323 ras 1718-1719

fixup protocol http 80

fixup protocol rsh 514

fixup protocol rtsp 554

fixup protocol sip 5060

fixup protocol sip udp 5060

fixup protocol skinny 2000

fixup protocol smtp 25

fixup protocol sqlnet 1521

fixup protocol tftp 69


access-list in_acl permit ip any any

access-list tor3 permit ip any any

pager lines 24

icmp permit any outside

icmp permit any inside

mtu outside 1500

mtu inside 1500

ip address outside 193.x.x.200

ip address inside 172.17.x.x.255.255.0

ip audit info action alarm

ip audit attack action alarm

pdm location inside

pdm location inside

pdm history enable

arp timeout 14400

global (outside) 1

nat (inside) 1 0 0

access-group tor3 in interface outside

route outside 1

timeout xlate 3:00:00

timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00

timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00

timeout uauth 0:05:00 absolute

aaa-server TACACS+ protocol tacacs+

aaa-server TACACS+ max-failed-attempts 3

aaa-server TACACS+ deadtime 10

aaa-server RADIUS protocol radius

aaa-server RADIUS max-failed-attempts 3

aaa-server RADIUS deadtime 10

aaa-server LOCAL protocol local

http server enable

http inside

no snmp-server location

no snmp-server contact

snmp-server community public

no snmp-server enable traps

floodguard enable

telnet timeout 5

ssh timeout 5

console timeout 0

dhcprelay server outside

dhcprelay enable inside

dhcprelay setroute inside

terminal width 80


: end

DHCPRelay(config)# s debug

debug dhcprelay event



Re: Problems with DHCP relay on PIX

Hi .. the config seems OK .. I have noticed that the DHCP server ( is the same as the firewall's default gateway .. and so I guess you might be using a router as DHCP server is that right ..? On your PIX what is the output of

show dhcprelay statistics

If the output shows hits for DHCPDISCOVER DHCPREQUEST then you know the PIX is getting those packets and relaying them accordingly. Check your DHCP server and perhaps increase the DHCP time-out value on the PIX dhcprelay timeout seconds (default is 60 seconds)

If the above counters are 0 then the packets are definetely not reaching the firewall and so you would have to check whatever is between the clients and the firewall .. ie .. a switch perhaps.

I hope it helsp .. please rate if it does !!

New Member

Re: Problems with DHCP relay on PIX

Hi Fernando!

Indeed i 'am using a router as a DHCP server which was perfectly working when it was connected directly to client. The command shows 0 everywhere, this confirm the fact that the PIX did not react to

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