Hi Bill,
It's because of routing and the next-hop selection due to the longest match
and because PPP links by default install a host route for its adjacent peer
Virtual-Access Interfaces inherit information from Virtual-Templates
If we use this basic configuration:
hostname R1
interface Virtual-Template1
ip address 10.1.124.1 255.255.255.0
interface Serial0/0
no ip address
encapsulation frame-relay
frame-relay interface-dlci 102 ppp Virtual-Template1
hostname R2
interface Virtual-Template1
ip address 10.1.124.2 255.255.255.0
interface Serial0/0
no ip address
encapsulation frame-relay
frame-relay interface-dlci 201 ppp Virtual-Template1
frame-relay interface-dlci 204 ppp Virtual-Template1
hostname R4
interface Virtual-Template1
ip address 10.1.124.4 255.255.255.0
interface Serial0/0
no ip address
encapsulation frame-relay
frame-relay interface-dlci 402 ppp Virtual-Template1
R1#sh ip route | b Gateway
Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.1.124.2/32 is directly connected, Virtual-Access2
C 10.1.124.0/24 is directly connected, Virtual-Access2
R2#sh ip route | b Gateway
Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 10.1.124.4/32 is directly connected, Virtual-Access3
C 10.1.124.1/32 is directly connected, Virtual-Access2
C 10.1.124.0/24 is directly connected, Virtual-Access2
is directly connected, Virtual-Access3
R4#sh ip route | b Gateway
Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.1.124.2/32 is directly connected, Virtual-Access2
C 10.1.124.0/24 is directly connected, Virtual-Access2
If we were to consider the decisions made for a packet travelling from R1 to
R4 (e.g. on R1 we go ping 10.1.124.4)
At R1 10.1.124.4 is best (only) matched by 10.1.124.0/24 via Virtual-Access2
- so the packet goes through the PPP link hitting R2
At R2 10.1.124.4 is best matched by 10.1.124.4/32 via Virtual-Access3 - so
the packet goes through the PPP link R4
The return of the ping is similar
At R4 10.1.124.1 is best (only) matched by 10.1.124.0/24 via Virtual-Access2
- so the packet goes through the PPP link hitting R2
At R2 10.1.124.1 is best matched by 10.1.124.1/32 via Virtual-Access2 - so
the packet goes through the PPP link hitting R1
Hope that's of some help.
Cheers,
Adam
On Wed, Oct 12, 2011 at 10:41 PM, Bill Riley <[email protected]>wrote:
> Yes they are on the same subnet. When I do a trace route it does go to the
> HUB first and then to the spoke so it is not direct. Still trying to
> understand why it does that. Is it just inherent in the PPPoFR
> configuration?****
>
> ** **
>
> ** **
>
> *From:* Adam Booth [mailto:[email protected]]
> *Sent:* Tuesday, October 11, 2011 5:22 PM
> *To:* Bill Riley
> *Cc:* [email protected]
> *Subject:* Re: [OSL | CCIE_RS] IPExpert Vol1 6.9****
>
> ** **
>
> Hi Bill,
>
> I will assuming that on your routers the virtual-templates exist on the
> same subnet.
>
> If you do a show ip route on each of the routers you will see a connected
> route for the network the virtual-template is associated with and a /32
> route for the direct peer through the virtual-access interface
>
> Connectivity between spokes occurs via the hub and requires routing and
> relies on longest match rules and the ppp peer neighbor routes.
>
> For spoke to spoke, the spoke will send traffic to the hub, which then will
> have an exact match for the other spoke due to the ppp neighbor route and be
> able to select the appropriate virtual-access to reach the other spoke.
>
> If you perform a traceroute between spokes even though these are on the
> same subnet, you will see the hub as a hop to reach the other spoke.
>
> Cheers,
> Adam
>
> ****
>
> On Wed, Oct 12, 2011 at 5:39 AM, Bill Riley <[email protected]>
> wrote:****
>
>
>
> Why is it when I configure the DLCI's using PPP I get a fully meshed
> network
> and can ping all the spoke sites even though the local DLCI is only setup
> to
> reach the hub site of R2?
>
>
>
>
>
> _______________________________________________
> For more information regarding industry leading CCIE Lab training, please
> visit www.ipexpert.com
>
> Are you a CCNP or CCIE and looking for a job? Check out
> www.PlatinumPlacement.com****
>
> ** **
>
_______________________________________________
For more information regarding industry leading CCIE Lab training, please visit
www.ipexpert.com
Are you a CCNP or CCIE and looking for a job? Check out
www.PlatinumPlacement.com
