Cisco 877 ADSL DHCP FQDN

[jukkaholm]

Hello all,

I have problem with Cisco 877 ADSL connection.

sh version:

Cisco IOS Software, C870 Software (C870-ADVSECURITYK9-M), Version 12.4(4)T1, RELEASE SOFTWARE (fc4)

The problem is that when I try to get an IP address for the router (BVI 1) via DHCP it fails with:

*Feb 9 19:21:55.047: DHCP: Scan: bad FQDN option len 3

*Feb 9 19:21:55.047: DHCP: Error in pkt. punting

If I add vlan 1 to the same bridge group, clients connected to the fastethernet ports can get IP addresses from the ISP just fine.

This problem is with one ISP, the router works fine with other ISP. The difference between ISP:s is that the one that doesnt work includes in its DHCP packet option 81: FQDN with value 0000 0020. The other ISP doesnt have this option its DHCP reply.

So, I would like to be able to get public IP address for the router using DHCP.

Configuration:

!-----------------------

bridge irb

!

!

interface ATM0

no ip address

no atm ilmi-keepalive

dsl operating-mode itu-dmt

!

interface ATM0.1 multipoint

pvc bridging1 0/100

encapsulation aal5snap

!

bridge-group 1

!

interface FastEthernet0

!

interface FastEthernet1

!

interface FastEthernet2

!

interface FastEthernet3

!

interface Vlan1

no ip address

bridge-group 1

!

interface BVI1

ip address dhcp client-id Vlan1

!

ip classless

!

no ip http server

no ip http secure-server

!

!

control-plane

!

bridge 1 protocol ieee

bridge 1 route ip

!-----------------------

debug dhcp detail:

*Feb 9 19:21:55.015: DHCP: SDiscover attempt # 2 for entry:

*Feb 9 19:21:55.015: Temp IP addr: 0.0.0.0 for peer on Interface: BVI1

*Feb 9 19:21:55.015: Temp sub net mask: 0.0.0.0

*Feb 9 19:21:55.015: DHCP Lease server: 0.0.0.0, state: 1 Selecting

*Feb 9 19:21:55.015: DHCP transaction id: 1925

*Feb 9 19:21:55.015: Lease: 0 secs, Renewal: 0 secs, Rebind: 0 secs

*Feb 9 19:21:55.015: Next timer fires after: 00:00:04

*Feb 9 19:21:55.015: Retry count: 2 Client-ID: 0015.c653.cd1b

*Feb 9 19:21:55.015: Client-ID hex dump: 0015C653CD1B

*Feb 9 19:21:55.015: Hostname: Router

*Feb 9 19:21:55.015: DHCP: SDiscover: sending 275 byte length DHCP packet

*Feb 9 19:21:55.015: DHCP: SDiscover 275 bytes

*Feb 9 19:21:55.015: B'cast on BVI1 interface from 0.0.0.0

*Feb 9 19:21:55.047: DHCP: Received a BOOTREP pkt

*Feb 9 19:21:55.047: DHCP: Scan: Message type: DHCP Offer

*Feb 9 19:21:55.047: DHCP: Scan: Server ID Option: (correct DHCP server IP) = C1E51C1B

*Feb 9 19:21:55.047: DHCP: Scan: Lease Time: 7200

*Feb 9 19:21:55.047: DHCP: Scan: bad FQDN option len 3

*Feb 9 19:21:55.047: DHCP: Error in pkt. punting

*Feb 9 19:21:59.015: DHCP: SDiscover attempt # 3 for entry:

sorry for the long post, tried to use attachment function but it timed out ...

[pkhatri]

Hi,

This is related to cisco bug ID: CSCsb47557

At this point, there is no workaround except to get the DHCP server to return option 81 with domain-name.

This bug is supposed to be fixed in versions 12.4(4.4), 12.4(4.4)T, 12.3(14)YT01.

Hope that helps - pls rate the post if it does.

Paresh

[jukkaholm]

Thanks for the quick reply.

I dont have direct access to the IOS downloads but my product vendor informs me that the IOS I use is the latest that can be dowloaded.

I allready asked him to double check.

[pkhatri]

In that case, I'm afraid you will have to wait a few weeks until an IOS greater than the ones I specified is released for this platform.

Pls do rate posts that help.

Paresh

[tekha · Accepted solution]

I've just checked and your ISP is right, there is no newer IOS then 12.4-4.T1

But have thought about downgrading to 12.3-14.YT1? This is just an idea, I don't know if it works. But on the link that pkhatri supplied, it says that the problem is solved in 2.3-14.YT1.

It mat take a while before a new IOS in the 12.4 train arrives.

[jukkaholm]

After upgrading to 12.3(14)T1 the device now gets ip address with dhcp.

Now there is another problem. The line is terribly bad. Even ATM ping loses some packets. This might be problem with the ISP line, but on this case I am not absolutely certain.