PPPoA and simple routing problem...

jquintard · ‎10-08-2010

Hello,

I want to connect two ADSL links to my router (my actual configuration use one link and a Dialer with a PPPoE session).

I have no ATM interface on my router (2821) so I want to connect two modems (using PPPoA) on the switch module (HWIC-4ESW).

My first modem is configured with 172.16.1.2 as ip address, can you confirm this settings are correct (I have some doubt about the ip nat inside) :

interface FastEthernet0/0/0

description PortConnectedToMyFirstModem

spanning-tree portfast

interface Vlan1

ip address 172.16.0.1 255.255.255.0

ip route 0.0.0.0 0.0.0.0 172.16.0.2

ip nat inside source list 1 interface vlan 1 overload

For my second link, I have try to configure my router like this (I want to use a second VLAN for futur use) :

interface FastEthernet0/0/1

description PortConnectedToMySecondModem

switchport access vlan 2

spanning-tree portfast

interface Vlan2

description Vlan Modem Nerim2

ip address 172.16.1.1 255.255.255.0

ip route 0.0.0.0 0.0.0.0 172.16.1.2 2

But I can't ping 172.16.1.1 from the router. It's normal but how to solve this problem ?

Jerome

andrew.prince · ‎10-08-2010

I'm not sure why you have configured VLAN's on your 2821, they are not required

If you are going to used seperate class C IP subnets then just address the interfaces directly.

Just so I understand, you have 1 x 2821 router and 2 x ADSL modems?

Peter Paluch · ‎10-08-2010

Andrew,

Jerome needed to create the VLANs - note that his configuration examples and the problem description indicate he is using a HWIC-4ESW card. The VLANs themselves seem to be absolutely OK.

What I do not understand is the following statement:

But I can't ping 172.16.1.1 from the router. It's normal but how to solve this problem ?

Does that mean that the 2821 router cannot ping its own interface? If yes then I suggest verifying the following:

Whether the VLAN 2 exists indeed (using the show vlan-switch)
Whether the switchport on HWIC-4ESW assigned to the VLAN 2 is up/up (show interface Fa0/0/1)
What is the state of the interface VLAN2 - should also be up/up (show interface vlan2)
Whether the network 172.16.1.0/24 is in the routing table (show ip route)

Best regards,

Peter

andrew.prince · ‎10-09-2010

Hey Peter,

What I was trying to get at, obviously not very clearly was - any switch (physical or router module) then ports will default into VLAN 1?

If native is support - there are multiple options, IP unnumbered with loopbacks, Bridging & IRB, Static IP with HSRP etc.......

Since the module is a switch module, then I would assume that it can also be a non-switchport (non layer 2) = layer 3

Since this is all an assumption - if they can be layer 3 ports, no need for vlans, directly configure the 2 x class c IP subnets on the non layer 2 ports = no need for VLAN's.

All of the above is of course based on the assumption the HWIC-4ESW does (a) support native vlans and (b) support the conversion of a port into a dedicated layer 3 port.

JMTCW

Peter Paluch · ‎10-10-2010

Hello Andrew,

Oh, I see now what you had on your mind. Thanks for clarifying.

Regarding the native VLAN support - surely, the HWIC-4ESW does support the native VLAN. But I am not sure how that would actually help to solve the original post - the author seems to simply want connect two ISPs to the same router and have two different IP subnets to talk to the respective routers.

The HWIC-4ESW is a Layer2 switching module only. It does not support the no switchport command to make a port to be routed (note that even in multilayer switches supporting this command, it merely creates an internal separate VLAN allocated from the extended range for each such port and silently attributes the port to it). The IP address therefore cannot be connfigured on a port of the HWIC module directly.

Best regards,

Peter

andrew.prince · ‎10-10-2010

Again not being clear - if the module supports no vlans = native vlan, then the 2 interfaces can either be bound to 1 interface (say loopback or Bridge) then the 2 x isp modems can have the "same" internal IP addresing scheme facing the router.

Or the router can either be configured with HSRP or just an IP SLA to either provide failover or PBR to take advantage of having 2 x ISP links.

I suppose my posts are more of a deisgn fix, rather than fixing the current design.

Peter Paluch · ‎10-10-2010

Andrew,

Thanks again for the clarification (I tend to use the term native vlan only with particular regard to 802.1Q trunks).

Okay, the original author has not yet responded so let's wait whether he chooses any of the suggestions already given.

Best regards,

Peter