In some environments, it may be necessary to bundle multiple serial links to act as single link with aggregated bandwidth. This document describes how to configure Cisco 4500 routers to bundle four serial interfaces using a virtual-template interface.
This configuration can be used for routers connected over leased lines or routers that have the Channel Service Unit/Data Service Unit (CSU/DSU). You can add additional features to this configuration depending on your needs.
There are no specific requirements for this document.
The information in this document is based on the software and hardware versions below.
Cisco 4500 routers in a lab environment with cleared configurations.
Cisco IOS® version 12.2(10b) was running on both routers.
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
This configuration can also be used with the following hardware and software versions.
Any two routers with four serial interfaces each.
WIC-1T and WIC-2T serial interfaces can be used.
For more information on document conventions, see the Cisco Technical Tips Conventions.
In this section, you are presented with the information to configure the features described in this document.
Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .
This document uses the network setup shown in the diagram below.
This configuration was tested using Cisco IOS Software Release 12.2(10b) on 4500 series routers. The same configuration concepts apply to a similar router topology or other Cisco IOS releases.
This document uses the configurations shown below.
RouterA |
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version 12.2 ! hostname RouterA ! ! username RouterB password xxx ip subnet-zero multilink virtual-template 1 ! interface loopback 0 ip address 192.168.1.1 255.255.255.0 ! interface Virtual-Template1 ip unnumbered loopback0 ppp authentication chap ppp multilink ! interface Serial0 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial1 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial2 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial3 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface FastEthernet0 ip address 10.17.1.254 255.255.255.0 ! router rip network 10.0.0.0 network 192.168.1.0 ! end |
RouterB |
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version 12.2 ! hostname RouterB ! username RouterA password xxx ip subnet-zero multilink virtual-template 1 ! interface loopback 0 ip address 192.168.1.2 255.255.255.0 ! ! interface Virtual-Template1 ip unnumbered loopback0 ppp authentication chap ppp multilink ! interface Serial0 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial1 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial2 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Serial3 no ip address encapsulation ppp no fair-queue ppp multilink pulse-time 3 ! interface Ethernet0 ip address 172.16.1.1 255.255.0.0 ! router rip network 172.16.0.0 network 192.168.1.0 ! end |
Configure the following to implement the above configuration:
multilink virtual-template
interface virtual-template
PPP multilink in each of the serial interfaces in which bundling has to be done.
An RIP as the IP routing protocol
Interface loopback 0 is configured so that it never fails, and ip unnumbered loopback 0 enhances the bundling of more than five serial interfaces with the same IP address.
When all the serial interfaces are up, and user traffic is to be sent, multilink PPP creates a virtual-access interface and the PPP negotiation takes place. The configuration for this virtual-access interface is cloned from the virtual template. The number of serial interfaces that are up are bundled in this virtual-access interface and an aggregate bandwidth is created.
This section provides information you can use to confirm your configuration is working properly.
Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.
show ip route
show ip rip database
show ppp multilink
show interface virtual-access 1
RouterA#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 172.16.0.0/16 [120/1] via 192.168.1.2, 00:00:19, Virtual-Access1 10.0.0.0/24 is subnetted, 1 subnets C 10.17.1.0 is directly connected, FastEthernet0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.0/24 is directly connected, Loopback0 C 192.168.1.2/32 is directly connected, Virtual-Access1 RouterA#show ip route connected 10.0.0.0/24 is subnetted, 1 subnets C 10.17.1.0 is directly connected, FastEthernet0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.0/24 is directly connected, Loopback0 C 192.168.1.2/32 is directly connected, Virtual-Access1 RouterB#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set C 172.16.0.0/16 is directly connected, Ethernet0 R 10.0.0.0/8 [120/1] via 192.168.1.1, 00:00:18, Virtual-Access1 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.1/32 is directly connected, Virtual-Access1 C 192.168.1.0/24 is directly connected, Loopback0 RouterB#show ip route connected C 172.16.0.0/16 is directly connected, Ethernet0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.1/32 is directly connected, Virtual-Access1 C 192.168.1.0/24 is directly connected, Loopback0 RouterA#show ip rip database 10.0.0.0/8 auto-summary 10.17.1.0/24 directly connected, FastEthernet0 172.16.0.0/16 auto-summary 172.16.0.0/16 [1] via 192.168.1.2, 00:00:34, Virtual-Access1 192.168.1.0/24 auto-summary 192.168.1.0/24 directly connected, Loopback0 192.168.1.2/32 directly connected, Virtual-Access1 RouterB#show ip rip database 10.0.0.0/8 auto-summary 10.0.0.0/8 [1] via 192.168.1.1, 00:00:13, Virtual-Access 1172.16.0.0/16 auto-summary 172.16.0.0/16 directly connected, Ethernet0 192.168.1.0/24 auto-summary 192.168.1.0/24 directly connected, Loopback0 192.168.1.1/32 directly connected, Virtual-Access1 RouterA#show ppp multilink Virtual-Access1, bundle name is RouterB Bundle up for 17:01:59 0 lost fragments, 0 reordered, 0 unassigned 0 discarded, 0 lost received, 1/255 load 0xD3C received sequence, 0x1180 sent sequence Member links: 4 (max not set, min not set) Serial0, since 17:01:59, last rcvd seq 000D38 Serial1, since 17:01:50, last rcvd seq 000D39 Serial2, since 17:01:46, last rcvd seq 000D3A Serial3, since 17:01:41, last rcvd seq 000D3B RouterB#show ppp multilink Virtual-Access1, bundle name is RouterA Bundle up for 12:47:33 0 lost fragments, 0 reordered, 0 unassigned 0 discarded, 0 lost received, 1/255 load 0x1186 received sequence, 0xD40 sent sequence Member links: 4 (max not set, min not set) Serial0, since 12:47:33, last rcvd seq 001184 Serial1, since 12:47:27, last rcvd seq 001185 Serial2, since 12:47:23, last rcvd seq 001182 Serial3, since 12:47:20, last rcvd seq 001183 RouterA#show interface virtual-access 1 Virtual-Access1 is up, line protocol is up Hardware is Virtual Access interface Interface is unnumbered. Using address of Loopback0 (192.168.1.1) MTU 1500 bytes, BW 6176 Kbit, DLY 100000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) DTR is pulsed for 5 seconds on reset LCP Open, multilink Open Open: IPCP Last input 00:00:00, output never, output hang never Last clearing of "show interface" counters 17:05:41 Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 1711 packets input, 163898 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 2256 packets output, 211897 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 output buffer failures, 0 output buffers swapped out 0 carrier transitions RouterB#show interface virtual-access 1 Virtual-Access1 is up, line protocol is up Hardware is Virtual Access interface Interface is unnumbered. Using address of Loopback0 (192.168.1.2) MTU 1500 bytes, BW 6176 Kbit, DLY 100000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) DTR is pulsed for 5 seconds on reset LCP Open, multilink Open Open: IPCP Last input 00:00:20, output never, output hang never Last clearing of "show interface" counters 12:54:17 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue :0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 2256 packets input, 216460 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 1714 packets output, 160624 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 output buffer failures, 0 output buffers swapped out 0 carrier transitions
This section provides information you can use to troubleshoot your configuration.
Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.
Note: Before issuing debug commands, please see Important Information on Debug Commands.
debug ppp negotiation - To see if a client is passing PPP negotiation; this command is used to check for address negotiation.
debug ppp authentication - To see if a client is passing authentication. If you are using a Cisco IOS Software Release prior to 11.2, use the debug ppp chap command instead.
debug ppp error - To display protocol errors and error statistics associated with PPP connection negotiation and operation.
debug vtemplate - To display the Virtual Template cloning to form a Virtual Access interface.
debug ppp multilink events - To see PPP multilink events debugging. Displays information about events affecting multilink groups.
show ppp multilink - To see the members of the multilink bundle.
The following outputs were obtained from the Cisco 4500 routers. They show the routers establishing a multilink PPP connection.
RouterA#debug vtemplate Virtual Template debugging is on *Dec 1 17:24:16.519: Vi1 VTEMPLATE: Reuse Vi1, recycle queue size 0 *Dec 1 17:24:16.519: Vi1 VTEMPLATE: Set default settings with ip unnumbered *Dec 1 17:24:16.539: Vi1 VTEMPLATE: Hardware address 00d0.bbfa.f579 *Dec 1 17:24:16.543: Vi1 VTEMPLATE: Has a new cloneblk vtemplate, now it has vtemplate *Dec 1 17:24:16.543: Vi1 VTEMPLATE: ********** CLONE VACCESS1 *********** *Dec 1 17:24:16.543: Vi1 VTEMPLATE: Clone from Virtual-Template1 interface Virtual-Access1 default ip address no ip address encap ppp ip unnumbered loopback0 end *Dec 1 17:24:16.595: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up *Dec 1 17:24:17.515: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up *Dec 1 17:24:17.595: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up RouterA#debug ppp negotiation PPP protocol negotiation debugging is on Dec 11 19:39:14.523: %LINK-5-CHANGED: Interface Serial0, changed state to reset Dec 11 19:39:14.523: Se0 LCP: State is Closed Dec 11 19:39:14.627: %SYS-5-CONFIG_I: Configured from console by console Dec 11 19:39:16.523: %LINK-3-UPDOWN: Interface Serial0, changed state to up Dec 11 19:39:16.523: Se0 PPP: Treating connection as a dedicated line Dec 11 19:39:16.523: Se0 PPP: Phase is ESTABLISHING, Active Open [0 sess, 1 load] Dec 11 19:39:16.523: Se0 LCP: O CONFREQ [Closed] id 25 len 24 Dec 11 19:39:16.523: Se0 LCP: MagicNumber 0xD4CBA693 (0x0506D4CBA693) Dec 11 19:39:16.523: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:39:16.523: Se0 LCP: EndpointDisc 1 RouterA (0x130A01506F6D65726F6C) Dec 11 19:39:16.535: Se0 LCP: I CONFREQ [REQsent] id 33 len 25 Dec 11 19:39:16.535: Se0 LCP: MagicNumber 0x03200E36 (0x050603200E36) Dec 11 19:39:16.535: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:39:16.539: Se0 LCP: EndpointDisc 1 RouterB (0x130B0150756C6C69676E79) Dec 11 19:39:16.539: Se0 LCP: O CONFACK [REQsent] id 33 len 25 Dec 11 19:39:16.539: Se0 LCP: MagicNumber 0x03200E36 (0x050603200E36) Dec 11 19:39:16.539: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:39:16.539: Se0 LCP: EndpointDisc 1 RouterB (0x130B0150756C6C69676E79) Dec 11 19:39:16.539: Se0 LCP: I CONFACK [ACKsent] id 25 len 24 Dec 11 19:39:16.539: Se0 LCP: MagicNumber 0xD4CBA693 (0x0506D4CBA693) Dec 11 19:39:16.539: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:39:16.543: Se0 LCP: EndpointDisc 1 RouterA (0x130A01506F6D65726F6C) Dec 11 19:39:16.543: Se0 LCP: State is Open Dec 11 19:39:16.543: Se0 PPP: Phase is VIRTUALIZED [0 sess, 1 load] Dec 11 19:39:16.555: Vi1 PPP: Phase is DOWN, Setup [0 sess, 1 load] Dec 11 19:39:16.587: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up Dec 11 19:39:16.587: Vi1 PPP: Treating connection as a dedicated line Dec 11 19:39:16.587: Vi1 PPP: Phase is ESTABLISHING, Active Open [0 sess, 1 load] Dec 11 19:39:16.587: Vi1 LCP: O CONFREQ [Closed] id 1 len 29 Dec 11 19:39:16.587: Vi1 LCP: AuthProto CHAP (0x0305C22305) Dec 11 19:39:16.587: Vi1 LCP: MagicNumber 0xD4CBA6D4 (0x0506D4CBA6D4) Dec 11 19:39:16.587: Vi1 LCP: MRRU 1524 (0x110405F4) Dec 11 19:39:16.587: Vi1 LCP: EndpointDisc 1 RouterA (0x130A01506F6D65726F6C) Dec 11 19:39:16.587: Vi1 PPP: Phase is UP [0 sess, 1 load] Dec 11 19:39:16.591: Vi1 IPCP: O CONFREQ [Closed] id 1 len 10 Dec 11 19:39:16.591: Vi1 IPCP: Address 192.168.1.1 (0x0306C0A80101) Dec 11 19:39:16.591: Vi1 MLP: Added first link Se0 to bundle RouterB Dec 11 19:39:16.623: Vi1 IPCP: I CONFREQ [REQsent] id 1 len 10 Dec 11 19:39:16.623: Vi1 IPCP: Address 192.168.1.2 (0x0306C0A80102) Dec 11 19:39:16.623: Vi1 IPCP: O CONFACK [REQsent] id 1 len 10 Dec 11 19:39:16.623: Vi1 IPCP: Address 192.168.1.2 (0x0306C0A80102) Dec 11 19:39:16.623: Vi1 IPCP: I CONFACK [ACKsent] id 1 len 10 Dec 11 19:39:16.627: Vi1 IPCP: Address 192.168.1.1 (0x0306C0A80101) Dec 11 19:39:16.627: Vi1 IPCP: State is Open Dec 11 19:39:16.627: Vi1 IPCP: Install route to 192.168.1.2 Dec 11 19:39:17.543: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up Dec 11 19:39:17.587: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up RouterB#debug ppp negotiation PPP protocol negotiation debugging is on Dec 11 19:38:08.975: Se0 LCP: I CONFREQ [Closed] id 25 len 24 Dec 11 19:38:08.975: Se0 LCP: MagicNumber 0xD4CBA693 (0x0506D4CBA693) Dec 11 19:38:08.975: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:38:08.975: Se0 LCP: EndpointDisc 1 RouterA (0x130A01506F6D65726F6C) Dec 11 19:38:08.975: Se0 LCP: Lower layer not up, Fast Starting Dec 11 19:38:08.975: Se0 PPP: Treating connection as a dedicated line Dec 11 19:38:08.979: Se0 PPP: Phase is ESTABLISHING, Active Open [0 sess, 1 load] Dec 11 19:38:08.979: Se0 LCP: O CONFREQ [Closed] id 33 len 25 Dec 11 19:38:08.979: Se0 LCP: MagicNumber 0x03200E36 (0x050603200E36) Dec 11 19:38:08.979: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:38:08.979: Se0 LCP: EndpointDisc 1 RouterB (0x130B0150756C6C69676E79) Dec 11 19:38:08.979: Se0 LCP: O CONFACK [REQsent] id 25 len 24 Dec 11 19:38:08.979: Se0 LCP: MagicNumber 0xD4CBA693 (0x0506D4CBA693) Dec 11 19:38:08.979: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:38:08.979: Se0 LCP: EndpointDisc 1 RouterA (0x130A01506F6D65726F6C) Dec 11 19:38:08.979: %LINK-3-UPDOWN: Interface Serial0, changed state to up Dec 11 19:38:08.987: Se0 LCP: I CONFACK [ACKsent] id 33 len 25 Dec 11 19:38:08.987: Se0 LCP: MagicNumber 0x03200E36 (0x050603200E36) Dec 11 19:38:08.987: Se0 LCP: MRRU 1524 (0x110405F4) Dec 11 19:38:08.987: Se0 LCP: EndpointDisc 1 RouterB (0x130B0150756C6C69676E79) Dec 11 19:38:08.987: Se0 LCP: State is Open Dec 11 19:38:08.987: Se0 PPP: Phase is VIRTUALIZED [0 sess, 1 load] Dec 11 19:38:08.999: Vi1 PPP: Phase is DOWN, Setup [0 sess, 1 load] Dec 11 19:38:09.039: Se0 IPCP: Packet buffered while building MLP bundle interface Dec 11 19:38:09.043: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up Dec 11 19:38:09.043: Vi1 PPP: Treating connection as a dedicated line Dec 11 19:38:09.043: Vi1 PPP: Phase is ESTABLISHING, Active Open [0 sess, 1 load] Dec 11 19:38:09.043: Vi1 LCP: O CONFREQ [Closed] id 1 len 30 Dec 11 19:38:09.043: Vi1 LCP: AuthProto CHAP (0x0305C22305) Dec 11 19:38:09.043: Vi1 LCP: MagicNumber 0x03200E78 (0x050603200E78) Dec 11 19:38:09.043: Vi1 LCP: MRRU 1524 (0x110405F4) Dec 11 19:38:09.043: Vi1 LCP: EndpointDisc 1 RouterB (0x130B0150756C6C69676E79) Dec 11 19:38:09.043: Vi1 PPP: Phase is UP [0 sess, 1 load] Dec 11 19:38:09.043: Vi1 IPCP: O CONFREQ [Closed] id 1 len 10 Dec 11 19:38:09.043: Vi1 IPCP: Address 192.168.1.2 (0x0306C0A80102) Dec 11 19:38:09.047: Vi1 MLP: Added first link Se0 to bundle RouterA Dec 11 19:38:09.047: Vi1 PPP: Pending ncpQ size is 1 Dec 11 19:38:09.047: Se0 IPCP: Redirect packet to Vi1 Dec 11 19:38:09.047: Vi1 IPCP: I CONFREQ [REQsent] id 1 len 10 Dec 11 19:38:09.047: Vi1 IPCP: Address 192.168.1.1 (0x0306C0A80101) Dec 11 19:38:09.047: Vi1 IPCP: O CONFACK [REQsent] id 1 len 10 Dec 11 19:38:09.047: Vi1 IPCP: Address 192.168.1.1 (0x0306C0A80101) Dec 11 19:38:09.051: Vi1 IPCP: I CONFACK [ACKsent] id 1 len 10 Dec 11 19:38:09.051: Vi1 IPCP: Address 192.168.1.2 (0x0306C0A80102) Dec 11 19:38:09.051: Vi1 IPCP: State is Open Dec 11 19:38:09.051: Vi1 IPCP: Install route to 192.168.1.1 Dec 11 19:38:09.987: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up Dec 11 19:38:10.043: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up RouterB#debug ppp multilink events Multilink events debugging is on Dec 11 19:41:30.239: %LINK-3-UPDOWN: Interface Serial0, changed state to up Dec 11 19:41:30.243: Se0 MLP: Request add link to bundle Dec 11 19:41:30.243: Se0 MLP: Adding link to bundle Dec 11 19:41:30.255: Vi1 MLP: VP: Clone from Vtemplate 1 block=1 Dec 11 19:41:30.299: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up Dec 11 19:41:30.299: Vi1 MLP: Added first link Se0 to bundle RouterA Dec 11 19:41:31.243: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up Dec 11 19:41:31.243: Se0 MLP: cdp packet forwarded to wrong interface Dec 11 19:41:31.299: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
Revision | Publish Date | Comments |
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1.0 |
15-Sep-2005 |
Initial Release |