DHCP on Cisco 881 WAN interface

Unanswered Question
Nov 20th, 2009

Greetings,

I'm working with a service provider (Telus in Canada) that can only supply an IP address for my Cisco 881 WAN interface via DHCP.  I'm use to ordering business class DSL service with some number of static IP address to use.  In this case - I'm suppose to register the WAN interface MAC address on their site - which will in turn provide a static IP out of the DHCP pool.  So in essence - I should get a static IP via DHCP.

The problem I'm having is when I set the WAN interface as follows:

interface FastEthernet4

ip address dhcp

ip verify unicast reverse-path

no ip redirects

no ip unreachables

no ip proxy-arp

ip flow ingress

ip virtual-reassembly

duplex auto

speed auto

snmp trap ip verify drop-rate

I do not get an IP address.

They will not support this setup, but I don't know how or what the many possibilities there are for configuring the 881 to pull an IP address.

HELP!!

I have this problem too.
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Brent Rockburn Fri, 11/20/2009 - 11:52

Can we see the debug output

I've add to use their site to regirster mac addresses before as well .. it will show you what the IP will be. You might have to remove it and re add it.

Also as a test you can create a vlan interface and put one of the physical interfaces into that vlan and put the DHCP entries on that interface and try it as well.

Let me know what happens.

iholdings Fri, 11/20/2009 - 12:01

Sorry - I'm a bit of a noob.  I've never dealt with any other IP addressing other than applying statics.

How do I set up debug?

When you say remove and re-add - would that be removing and re-adding the MAC (for int Fa4) to the IP on the Telus site?

Brent Rockburn Fri, 11/20/2009 - 12:06

No worries man ... no worries at all ..

# debug dhcp detail

I meant remove it from the telus site and re add it.

Also, is it an older dsl modem? Because I've seen problems with that as well.

When you regirstered the MAC for fas4 did you get any errors?

I can send you what i used as a config if you'd like.

let me know

Bye for now.

iholdings Fri, 11/20/2009 - 12:12

A sample config would be great!!

I just went and removed/re-added the Fa4 MAC - got no errors (took defaults for Host Name and Domain) and got a completely different static address. reloaded the router - but still no IP.

Can I force a command to show debug output?

Brent Rockburn Fri, 11/20/2009 - 12:16

#term mon <-- This will send the output of your debug command to your terminal screen. use #term no mon to shut it off and use "#undebug all" to shut off the debug.

I'll send you the config as soon as I can find it, shouldn't be long.

iholdings Fri, 11/20/2009 - 12:25

Here's the debug output.  I really appreciate your help on this.  Very frustrating.

000897: *Nov 20 12:21:27.011 PCTime: DHCP: Try 3 to acquire address for FastEthernet4

000898: *Nov 20 12:21:27.011 PCTime: DHCP: allocate request

000899: *Nov 20 12:21:27.011 PCTime: DHCP: zapping entry in DHC_PURGING state for Fa4

000900: *Nov 20 12:21:27.011 PCTime: DHCP: deleting entry 85AC0D64 0.0.0.0 from list

000901: *Nov 20 12:21:27.011 PCTime: Temp IP addr: 0.0.0.0  for peer on Interface: FastEthernet4

000902: *Nov 20 12:21:27.011 PCTime: Temp  sub net mask: 0.0.0.0

000903: *Nov 20 12:21:27.011 PCTime:    DHCP Lease server: 0.0.0.0, state: 11 Purging

000904: *Nov 20 12:21:27.011 PCTime:    DHCP transaction id: 16DF

000905: *Nov 20 12:21:27.011 PCTime:    Lease: 0 secs,  Renewal: 0 secs,  Rebind: 0 secs

000906: *Nov 20 12:21:27.011 PCTime:    Next timer fires after: 00:00:21

000907: *Nov 20 12:21:27.011 PCTime:    Retry count: 0   Client-ID: cisco-0024.c40a.c0aa-Fa4

000908: *Nov 20 12:21:27.011 PCTime:    Client-ID hex dump: 636973636F2D303032342E633430612E

000909: *Nov 20 12:21:27.011 PCTime:                        633061612D466134

000910: *Nov 20 12:21:27.011 PCTime:    Hostname: Calgary

000911: *Nov 20 12:21:27.011 PCTime: DHCP: new entry. add to queue, interface FastEthernet4

000912: *Nov 20 12:21:27.011 PCTime: DHCP: SDiscover attempt # 1 for entry:

000913: *Nov 20 12:21:27.011 PCTime: Temp IP addr: 0.0.0.0  for peer on Interface: FastEthernet4

000914: *Nov 20 12:21:27.011 PCTime: Temp  sub net mask: 0.0.0.0

000915: *Nov 20 12:21:27.011 PCTime:    DHCP Lease server: 0.0.0.0, state: 3 Selecting

000916: *Nov 20 12:21:27.011 PCTime:    DHCP transaction id: 16E0

000917: *Nov 20 12:21:27.011 PCTime:    Lease: 0 secs,  Renewal: 0 secs,  Rebind: 0 secs

000918: *Nov 20 12:21:27.011 PCTime:    Next timer fires after: 00:00:04

000919: *Nov 20 12:21:27.011 PCTime:    Retry count: 1   Client-ID: cisco-0024.c40a.c0aa-Fa4

000920: *Nov 20 12:21:27.011 PCTime:    Client-ID hex dump: 636973636F2D303032342E633430612E

000921: *Nov 20 12:21:27.011 PCTime:                        633061612D466134

000922: *Nov 20 12:21:27.011 PCTime:    Hostname: Calgary

000923: *Nov 20 12:21:27.011 PCTime: DHCP: SDiscover: sending 294 byte length DHCP packet

000924: *Nov 20 12:21:27.011 PCTime: DHCP: SDiscover 294 bytes

000925: *Nov 20 12:21:27.015 PCTime:             B'cast on FastEthernet4 interface from 0.0.0.0

000926: *Nov 20 12:21:30.967 PCTime: DHCP: SDiscover attempt # 2 for entry:

000927: *Nov 20 12:21:30.967 PCTime: Temp IP addr: 0.0.0.0  for peer on Interface: FastEthernet4

000928: *Nov 20 12:21:30.967 PCTime: Temp  sub net mask: 0.0.0.0

000929: *Nov 20 12:21:30.967 PCTime:    DHCP Lease server: 0.0.0.0, state: 3 Selecting

000930: *Nov 20 12:21:30.967 PCTime:    DHCP transaction id: 16E0

000931: *Nov 20 12:21:30.967 PCTime:    Lease: 0 secs,  Renewal: 0 secs,  Rebind: 0 secs

000932: *Nov 20 12:21:30.967 PCTime:    Next timer fires after: 00:00:04

000933: *Nov 20 12:21:30.967 PCTime:    Retry count: 2   Client-ID: cisco-0024.c40a.c0aa-Fa4

000934: *Nov 20 12:21:30.967 PCTime:    Client-ID hex dump: 636973636F2D303032342E633430612E

000935: *Nov 20 12:21:30.967 PCTime:                        633061612D466134

000936: *Nov 20 12:21:30.967 PCTime:    Hostname: Calgary

000937: *Nov 20 12:21:30.967 PCTime: DHCP: SDiscover: sending 294 byte length DHCP packet

000938: *Nov 20 12:21:30.967 PCTime: DHCP: SDiscover 294 bytes

000939: *Nov 20 12:21:30.967 PCTime:             B'cast on FastEthernet4 interface from 0.0.0.0

000940: *Nov 20 12:21:34.967 PCTime: DHCP: SDiscover attempt # 3 for entry:

000941: *Nov 20 12:21:34.967 PCTime: Temp IP addr: 0.0.0.0  for peer on Interface: FastEthernet4

000942: *Nov 20 12:21:34.967 PCTime: Temp  sub net mask: 0.0.0.0

000943: *Nov 20 12:21:34.967 PCTime:    DHCP Lease server: 0.0.0.0, state: 3 Selecting

000944: *Nov 20 12:21:34.967 PCTime:    DHCP transaction id: 16E0

000945: *Nov 20 12:21:34.967 PCTime:    Lease: 0 secs,  Renewal: 0 secs,  Rebind: 0 secs

000946: *Nov 20 12:21:34.967 PCTime:    Next timer fires after: 00:00:04

000947: *Nov 20 12:21:34.967 PCTime:    Retry count: 3   Client-ID: cisco-0024.c40a.c0aa-Fa4

000948: *Nov 20 12:21:34.967 PCTime:    Client-ID hex dump: 636973636F2D303032342E633430612E

000949: *Nov 20 12:21:34.967 PCTime:                        633061612D466134

000950: *Nov 20 12:21:34.967 PCTime:    Hostname: Calgary

000951: *Nov 20 12:21:34.967 PCTime: DHCP: SDiscover: sending 294 byte length DHCP packet

000952: *Nov 20 12:21:34.967 PCTime: DHCP: SDiscover 294 bytes

000953: *Nov 20 12:21:34.967 PCTime:             B'cast on FastEthernet4 interface from 0.0.0.0

000954: *Nov 20 12:21:38.967 PCTime: DHCP: QScan: Timed out Selecting state%Unknown DHCP problem.. No allocation possible

iholdings Mon, 11/23/2009 - 07:54

Hello-

Any luck finding the sample config.?  It looks like I'm stuck with Telus - so any help would be most appreciated.

Thanks.

PerogyOverload Tue, 01/19/2010 - 18:59

I realize this post is few months old at this point, but it comes up in a Google search for "telus cisco dhcp" which I came across today, so I thought I'd post my experience and hopefully some semblance of a resolution.

I was working on this same issue except with a Secure Router 520.  Before I registered the MAC address via http://registerdevice.telus.com, it grabbed a 10.137.x.x (non-externally routable) address (which is normal behaviour for Telus).  After registering the MAC address, it would not obtain an IP address what so ever.  Telus tech support insisted there was nothing wrong on their end, but couldn't explain why I got an address prior to registering, but not after.

After a lot of testing, what it boiled down to was this:

- it looks like Telus' DHCP servers are checking/enforcing the "hostname" parameter of a DHCP request in addition to the MAC address before handing out an IP.  Cisco's implementation of the DHCP client sends whatever the router has as its hostname if you just have "ip address dhcp" in the interface's config, unless you specify "ip address dhcp hostname " instead.

- other DHCP clients (such as in various Windows versions and other routers) have the option to also obtain the hostname from the DHCP server, which apparently Cisco's client won't do (or at least I can't find a way to make it do that).

- you can also set the hostname parameter in http://registerdevice.telus.com, or if you leave it blank it will auto-create one (something like S-17-xxx).

So, to resolve this issue (or, at least what worked for me):

a) in http://registerdevice.telus.com, make sure you register the *actual hostname* of your Cisco router (most likely it's also case-sensitive, although I didn't test that thoroughly) in addition to its MAC address.

or (not thoroughly tested by me)

b) make a note of what hostname was automatically generated for the router's MAC address in http://registerdevice.telus.com and change the router's external interface config to read "ip address dhcp hostname " (assuming you have a reasonably current IOS version - not sure exactly which version added the additional "ip address dhcp" syntax).

After I did step a) I ran "ip address dhcp" and immediately got the public "static" IP I was expecting.

Good luck!

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