Wednesday, 26 May 2010

Bundling Frame Relay Links

Frame-relay study time!

There are several ways to bundle links together in frame-relay:

  1. Frame-relay Multilink - FRF.16

  2. PPP Multilink


FRF16 requires configuration all along the path, so the service provider must support it. PPP multilink can be used on any frame-relay links and doesn't require anything from the SP.

Frame-relay Multilink - FRF.16


I'll be using the incredibly complicated topology shown below. To keep it simple the two routers are directly connected.


By default the "encapsulation frame-relay" command configures a device as a frame-relay DTE and two DTE's back-to-back won't talk. They'll both be sending LMI status enquiries but with no DCE to answer to tell them which DLCI is active, neither router will send any traffic. Using the "no keepalive" command brings the links up and stops the LMI messaging (which transmits every 6 keepalive cycles by default).


The configs are:


hostname R1
!
interface MFR1
ip address 192.168.0.1 255.255.255.0
no keepalive
frame-relay interface-dlci 100
!
interface Serial0/0
encapsulation frame-relay MFR1
clock rate 2000000
!
interface Serial0/1
encapsulation frame-relay MFR1
clock rate 2000000

hostname R2
!
interface MFR1
ip address 192.168.0.2 255.255.255.0
no keepalive
frame-relay interface-dlci 100
!
interface Serial0/0
encapsulation frame-relay MFR1
!
interface Serial0/1
encapsulation frame-relay MFR1


You can check the multilink status as below:

R1#show frame-relay multilink
Bundle: MFR1, State = up, class = A, fragmentation disabled
BID = MFR1
Bundle links:
Serial0/1, HW state = up, link state = Up, LID = Serial0/1
Serial0/0, HW state = up, link state = Up, LID = Serial0/0


PPP Multilink


In this case I've added a frame-relay switch in the middle.


It's providing two separate VCs and they are being bundled together at either end using PPP multilink. Configs are below:


hostname R1
!
interface Serial0/0
encapsulation frame-relay
frame-relay interface-dlci 102 ppp Virtual-Template1
!
interface Serial0/1
encapsulation frame-relay
frame-relay interface-dlci 304 ppp Virtual-Template1
!
interface Virtual-Template1
ip address 192.168.0.1 255.255.255.0
ppp multilink



hostname R2
!
interface Serial0/0
encapsulation frame-relay
frame-relay interface-dlci 201 ppp Virtual-Template1
!
interface Serial0/1
encapsulation frame-relay
frame-relay interface-dlci 403 ppp Virtual-Template1
!
interface Virtual-Template1
ip address 192.168.0.2 255.255.255.0
ppp multilink


Don't need to disable the keepalives now as there's a FR switch responding to LMI status queries.

To test the bundle, use "show ppp multilink". The Virtual-Access interfaces are randomly generated by PPP from the virtual-template and may not always be the same.

R1#show ppp multilink

Virtual-Access4, bundle name is R2
Endpoint discriminator is R2
Bundle up for 00:05:50, total bandwidth 200000, load 1/255
Receive buffer limit 24384 bytes, frag timeout 1000 ms
0/0 fragments/bytes in reassembly list
0 lost fragments, 0 reordered
0/0 discarded fragments/bytes, 0 lost received
0x2 received sequence, 0x2 sent sequence
Member links: 2 (max not set, min not set)
Vi1, since 00:05:50
Vi2, since 00:05:50
No inactive multilink interfaces

R1#show int vi1
Virtual-Access1 is up, line protocol is up
Hardware is Virtual Access interface
Internet address is 192.168.0.1/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP Open, multilink Open
Link is a member of Multilink bundle Virtual-Access4
PPPoFR vaccess, cloned from Virtual-Template1
Vaccess status 0x44
Bound to Serial0/0 DLCI 102, Cloned from Virtual-Template1, loopback not set

R1#show int vi2
Virtual-Access2 is up, line protocol is up
Hardware is Virtual Access interface
Internet address is 192.168.0.1/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP Open, multilink Open
Link is a member of Multilink bundle Virtual-Access4
PPPoFR vaccess, cloned from Virtual-Template1
Vaccess status 0x44
Bound to Serial0/1 DLCI 304, Cloned from Virtual-Template1, loopback not set





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