Cisco + Virgin Cable

11. June 2011 10:49

 

I seem to keep running into a problem with a cisco router (a cisco 877) with a virgin media connection. It would appear that part of virgin's network tends to break. I don't know the exact cause but from how I understand it. It is a fault with virgin somehow and some type of compatibility issue with cisco routers.

 

The problem for me tends to trigger when virgin has an issue inside their network or for some reason I have to disable the internet connection. When I bring the connection back up the cisco router can never successfully get an ip address by dhcp again. Until of course virgin is contacted and something is reset at their end. It will however allocate an ip address to a computer if you plug it directly into the virgin connection.

 

Here is how I was debugging the issue. To start with put your cisco terminl connection into monitor mode and debug dhcp (after you become an enabled user of course). Like this

 

Cisco#terminal monitor
Cisco#debug dhcp

 

This will cause you to see output like the following.

 

Jun  6 08:51:39.998: DHCP: deleting entry 83D002B8 0.0.0.0 from list
Jun  6 08:52:09.437: DHCP: Try 15 to acquire address for Vlan2
Jun  6 08:52:09.441: DHCP: allocate request
Jun  6 08:52:09.445: DHCP: new entry. add to queue, interface Vlan2
Jun  6 08:52:09.445: DHCP: SDiscover attempt # 1 for entry:
Jun  6 08:52:09.445: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:52:09.445: DHCP: SDiscover 290 bytes
Jun  6 08:52:09.445:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:52:13.006: DHCP: SDiscover attempt # 2 for entry:
Jun  6 08:52:13.006: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:52:13.006: DHCP: SDiscover 290 bytes
Jun  6 08:52:13.006:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:52:17.006: DHCP: SDiscover attempt # 3 for entry:
Jun  6 08:52:17.006: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:52:17.006: DHCP: SDiscover 290 bytes
Jun  6 08:52:17.006:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:52:28.568: DHCP: Received a BOOTREP pkt Not for us..:  xid: 0x3E466ABF%Unknown DHCP problem.. No allocation possible
Jun  6 08:52:29.924: DHCP: Waiting for 60 seconds on interface Vlan2

 

 

Unfortunatly the information is not very forthcoming with anything that matters. Since virgin is not actually replying to any dhcp requests with anything! So the next step to try is to reboot the cable modem etc... Of course it will just keep repeating the same output as above and virgin will continue to ignore any dhcp requests for some reason.

 

The next part of this is to phone virgin. Tell them specificly that the router is not allocating an address. They will then head off do some checks make sure they can talk to the cable modem directly and quitly reset something. Of course on the next attempt you can then expect some sort of success.

 

 

Jun  6 08:57:31.489: DHCP: Try 19 to acquire address for Vlan2
Jun  6 08:57:31.493: DHCP: allocate request
Jun  6 08:57:31.497: DHCP: new entry. add to queue, interface Vlan2
Jun  6 08:57:31.497: DHCP: SDiscover attempt # 1 for entry:
Jun  6 08:57:31.497: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:57:31.497: DHCP: SDiscover 290 bytes
Jun  6 08:57:31.497:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:57:35.106: DHCP: SDiscover attempt # 2 for entry:
Jun  6 08:57:35.106: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:57:35.106: DHCP: SDiscover 290 bytes
Jun  6 08:57:35.106:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:57:39.106: DHCP: SDiscover attempt # 3 for entry:
Jun  6 08:57:39.106: DHCP: SDiscover: sending 290 byte length DHCP packet
Jun  6 08:57:39.106: DHCP: SDiscover 290 bytes
Jun  6 08:57:39.106:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:57:39.154: DHCP: Received a BOOTREP pkt
Jun  6 08:57:39.154: DHCP: offer received from 62.31.64.115
Jun  6 08:57:39.154: DHCP: SRequest attempt # 1 for entry:
Jun  6 08:57:39.154: DHCP: SRequest- Server ID option: 62.31.64.115
Jun  6 08:57:39.154: DHCP: SRequest- Requested IP addr option: x.x.x.x
Jun  6 08:57:39.154: DHCP: SRequest placed lease len option: 603658
Jun  6 08:57:39.154: DHCP: SRequest: 308 bytes
Jun  6 08:57:39.154: DHCP: SRequest: 308 bytes
Jun  6 08:57:39.154:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:57:42.110: DHCP: SRequest attempt # 2 for entry:
Jun  6 08:57:42.110: DHCP: SRequest- Server ID option: 62.31.64.115
Jun  6 08:57:42.110: DHCP: SRequest- Requested IP addr option: x.x.x.x
Jun  6 08:57:42.110: DHCP: SRequest placed lease len option: 603658
Jun  6 08:57:42.110: DHCP: SRequest: 308 bytes
Jun  6 08:57:42.110: DHCP: SRequest: 308 bytes
Jun  6 08:57:42.110:             B'cast on Vlan2 interface from 0.0.0.0
Jun  6 08:57:42.347: DHCP: Received a BOOTREP pkt
Jun  6 08:57:46.347: DHCP Client Pooling: ***Allocated IP address: x.x.x.x
Jun  6 08:57:46.351: Allocated IP address = x.x.x.x  255.255.255.240

 

 

Finally it gets an ip address. The reason why I suspect this is a problem inside the virgin network is simple. Evertime I have to take the connection offline I can do it by a shutdown of the interface (the easy method) or by rebooting the cisco or some such. This problem occurs in exactly the same way. However the following at the site end of things never changes.

 

  • The cisco will still manage to get an ip address without being restarted.
  • The cisco config has not changed in any way.

 

To make matters worse. Virgin are not capable of allocating a static ip address to the connection. their definition of static is still allocated by dhcp. So there is no way around this problem.

 

I guess its just one of thoose things that will never be fixed by virgin media. I think this is a virgin media issue. What do you think?

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Comments (11) -

6/16/2011 9:14:06 AM #

I'm seeing a similar thing but have never actually got an address on an 1861. What firmware are you using on the 877?

ionic United Kingdom |

6/16/2011 9:40:32 AM #


Firmware version I am using is c870-advipservicesk9-mz.124-15.T10.bin

If you never actually get an ip address try toggling the option

no ip dhcp-client broadcast-flag

james United Kingdom |

6/16/2011 10:01:32 AM #

c1861-advipservicesk9-mz.124-24.T3.bin here

As I've mentioned on TBB I'm going to do some serious digging next week once a separate router's arrived on site.

ionic United Kingdom |

6/22/2011 6:25:32 PM #

Did you ever get anywhere with this?

I've just had Virgin Media cable installed this afternoon, and am hitting what looks like the same issue.

As far as I can tell, my router is sending out DHCP packets with a transaction ID of (for example) 0x1d54, but the reply that comes back from Virgin Media has a transaction ID of (e.g.) 0xda5851f3 - hence the "not for us" debug message.

I'm still within my 28 days, so able to cancel my Virgin Media connection if it really doesn't work - but it's frustrating to be so close and yet so far!

(James - feel free to email me, I'd like to chat on the phone! Smile)

Jonathan United Kingdom |

6/22/2011 6:35:48 PM #


Never got any further with it. The problem has not occured again since it got an ip address. Unfortunately for me the connection isn't local its around 300 miles away so it is hard to get at to capture a dump.

If you could capture a dump of traffic using linux or win pcap or some such then we would have something to go on.

James United Kingdom |

7/18/2011 3:33:35 PM #


I've just been sent a new cable modem by Virgin media after the old one went the way of the Dodo.  I didn't opt for the super-hub as I have (had) a perfectly usable Linksys router/WAP and (b)the super-hub is butt ugly.

Now, after activiating the new modem (via India - what a nightmare) the Linksys  won't see the MAC address of the new modem.  Rather, it is still hanging on to the MAC address of the OLD modem.  Subsequently no IP address is being obtained.

If I don't use the Linksys router and connect the VM modem direct to the PC, all works just fine so it would seem that all is actually well at VM's end.

I have a few things left to try to resolve this permanently.

- don't use Chrome browser to access the router's admin page.  Apparently, this is a known issue, so I'm going to try with IE and Firefox and see if the status page does actually save the new MAC address / IP address.

- have the modem and router on different power sources.  Bring the router up first and leave it for 10 mins or so before bring up the VM modem to see if it's a timing issue.

- a factory reset of the Linksys router (last resort)

It shouldn't be this painful, but it really hasn't helped that VM's call centre have been unhelpful. I appreciate they can't support all routers/WAPs but there must be certain issues (like this) they can advise on at a generalised level.

Missy United Kingdom |

12/2/2011 9:30:33 AM #

I can confirm the problem in the original post. Tried with three different Cisco routers. Also opened a TAC case with Cisco. The Virgin DHCP server does not respond with an address. Virgin Media will tell you the router "has an address" but what they mean is that an address has been assigned within their DHCP service.
It works if you plug a PC into the modem, so there must be a difference in the DHCP dialog, but a service that does not work with a Cisco router is not fit for purpose.

Anthony_ United Kingdom |

7/20/2012 3:07:26 PM #

Hi,

The fix to this is down to the way that the Virgin DHCP servers work and your will have it sent to unicast, enter the following at this will fix the issue:

ip dhcp-client broadcast-flag

Hope this helps

Colin Fletcher United Kingdom |

7/20/2012 5:22:14 PM #


That may appear to work but give it time. It will then work with the flag off again ;)

james United Kingdom |

8/15/2012 1:52:59 PM #

I had this problem and i can tell you why it's hard for a cisco router to receive a dhcp address! For security reason Virgin media will lock the mac address of the router they provide you with and when you put it into a modem mode and try to request ip address using a cisco router it will not give one, if it does then when it comes to renewing the ip address it might not renew. To fix the ISSUE NOTE THE MAC-ADDRESS OF THE NETGEAR OR ROUTER PROVIDED BY VIRIGIN MEDIA, THEN ON YOU CISCO ROUTER  ENTER THIS MAC ADDRESS ON THE INTERFACE CONNECTED TO VIRGIN MEDIA MODEM OR ROUTER OPERATING IN MODEM MODE. (remember you are forcing this mac address on the interface, this can always be undone, so it'safe). This will make it apppear to virgin media that the ip address request is coming from the correct mac-address and you should have no problem ever again receiving ip address via DHCP
I hope this HELPS!

Fredy () United Kingdom |

7/30/2013 5:11:13 PM #

Well I must say the circumstances here are all similar to mine, to the extent that I can undestand what you are saying.

I had a Panasonic printer, a PC, a Humax Fox T2 PVR, and my ntl cable modem all connected via a Fonera 2.0. DHCP was enabled everywhere, but everything was connecting to everything else as required. Then everything changed.

I just connected everything up the same (after a few weeks without) having done a reset of the modem from the config page. I could reach the PVR from the PC, but not the printer. The PC could only access the internet through the unecrypted SSID (not the encrypted and not down the cat 5). The PVR could reach the PC but not the internet (cabled only no wifi at the PVR). I cannot get to the router config page.

I acquired a "2 wire" BT router and had similar problems with only some connections through the router working.

It's obvious even to me that things weren't working as they had't been given IP addresses. I tampered with fixed IP, but that just seemed to make things worse.

I phoned Virgin, but they claimed to trace a fault to the (ethernet) NIC in the PC. This doesn't make any sense to me as the PC works fine when connected by itself.

Any advice gratefully received.

Colin Newman United Kingdom |