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two links, one interface, vlans and dhcp

I have a router 2821 with two Internet links over "one" ethernet port. For this, I configured the interface GigabitEthernet0/1 in two subinterfaces with Vlans (interface GigabitEthernet0/1.998 and interface GigabitEthernet0/1.999). Betwen the router and the internet modens (ADSL and Cable) I have a Catalyst 2950T with the respective Vlans.

My problem is with the interface GigabitEthernet0/1.998 that is connected to cable modem (Motorola). This interface doesn´t receive IP address in the BVI interface via DHCP. If I place a workstation or the interface GigabitEthernet0/1 without Vlan configuration and switch the IP address is ok.

It has some suggestion, the problem is with the BVI interface or with the switch configuration (mac-address switch x mac-address router for the service provider)? What is the good design for this??

>>Confs router

interface GigabitEthernet0/1

no ip address

!

interface GigabitEthernet0/1.998

description "connected to WAN vlan ID 998 - Cable Modem"

encapsulation dot1Q 998

bridge-group 1

!

interface GigabitEthernet0/1.999

description "connected to WAN vlan ID 999 - ADSL"

encapsulation dot1Q 999

ip address 10.0.0.2 255.255.255.248

!

interface BVI1

ip address dhcp

>>Confs switch

interface FastEthernet0/17

description c2821 outside

switchport trunk allowed vlan 998,999

switchport mode trunk

!

interface FastEthernet0/18

description adsl

switchport access vlan 999

!

interface FastEthernet0/19

description cable

switchport access vlan 998

!

>>

Feb 9 03:00:28.685: Retry count: 2 Client-ID: cisco-0013.1a7f.0a89-BV1

Feb 9 03:00:28.685: Client-ID hex dump: 636973636F2D303031332E316137662E

Feb 9 03:00:28.685: 306138392D425631

Feb 9 03:00:28.685: Hostname: c2821

Feb 9 03:00:28.685: DHCP: SDiscover: sending 292 byte length DHCP packet

Feb 9 03:00:28.685: DHCP: SDiscover 292 bytes

Feb 9 03:00:28.685: B'cast on BVI1 interface from 0.0.0.0

Feb 9 03:00:31.497: DHCP: Received a BOOTREP pkt Not for us..: xid: 0x23ECA7F

Feb 9 03:00:32.685: DHCP: SDiscover attempt # 3 for entry:

Feb 9 03:00:32.685: Temp IP addr: 0.0.0.0 for peer on Interface: BVI1

Feb 9 03:00:32.685: Temp sub net mask: 0.0.0.0

Feb 9 03:00:32.685: DHCP Lease server: 0.0.0.0, state: 1 Selecting

Feb 9 03:00:32.685: DHCP transaction id: 1798

Feb 9 03:00:32.685: Lease: 0 secs, Renewal: 0 secs, Rebind: 0 secs

Feb 9 03:00:32.685: Next timer fires after: 00:00:04

Feb 9 03:00:32.685: Retry count: 3 Client-ID: cisco-0013.1a7f.0a89-BV1

Feb 9 03:00:32.685: Client-ID hex dump: 636973636F2D303031332E316137662E

Feb 9 03:00:32.685: 306138392D425631

Feb 9 03:00:32.685: Hostname: c2821

Feb 9 03:00:32.685: DHCP: SDiscover: sending 292 byte length DHCP packet

Feb 9 03:00:32.685: DHCP: SDiscover 292 bytes

Feb 9 03:00:32.685: B'cast on BVI1 interface from 0.0.0.0

Feb 9 03:00:36.685: DHCP: QScan: Timed out Selecting state

Feb 9 03:00:43.741: DHCP: Received a BOOTREP pkt Not for us..: xid: 0xA87C56C3

Feb 9 03:00:43.773: DHCP: Received a BOOTREP pkt Not for us..: xid: 0xA87C56C3%Unknown DHCP problem.. No allocation possible

Feb 9 03:00:45.821: DHCP: Waiting for 20 seconds on interface BVI1

Feb 9 03:00:47.381: DHCP: Received a BOOTREP pkt Not for us..: xid: 0xFF724762

Feb 9 03:00:49.737: DHCP: Received a BOOTREP pkt Not for us..: xid: 0x18D646E9

Feb 9 03:01:00.897: DHCP: Received a BOOTREP pkt Not for us..: xid: 0x5583DDD0

2 REPLIES
Purple

Re: two links, one interface, vlans and dhcp

Hi Gustavo,

Any particular reason you are bridging on that interface ? Why can't you get rid of the BVI and configure 'ip address dhcp' under interface GigabitEthernet0/1.998 ?

Paresh

New Member

Re: two links, one interface, vlans and dhcp

Bridging configuration because with the 'ip address dhcp' under interface GigabitEthernet0/1.998 doesn´t receive the ip address with the cable modem. If I place other dhcp server (Linux) with this configuration in the interface GigabitEthernet0/1.998 the IP address is ok. Bridging because cable modem.

With the BVI configuration, the dhcp client on the interface already received the IP, but after one or two days trying. In this midle time, the service provider doesn´t have allocated none IP and mac-address.

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