BGP link-bw & multipath Load Balancing « CCIE, the beginning!

28/02/2012 BGP link-bw & multipath Load Balancing « CCIE, the beginning!

1/17cciethebeginning.wordpress.com/2009/01/19/bgp-link-bw-multipath-load-balancing/

CCIE, the beginning!January 19, 2009

BGP linkbw & multipath Load Balancing

Filed under: BGP,Routing protocols — cciethebeginning @ 11:41 am Tags: BGP, Load Balancing 2 Votes

An autonomous system can be connected to another through multiple links and according to the companybusiness and redundancy requirements different schemes can be used:

Primary/secondary: where the second link is used only when the first link fails. Symmetric loadsharing: where the traffic is equally distributed among multiple links in the same time,

which provides a high level of redundancy for the enterprise.

But, it’s not always possible to provide equal bandwidth links because of either financial limits or availabilityof such solution. So the need to engineer traffic through these links according to their bandwidth capacity.

Here comes the solution of BGP link bandwidth.

With the deployment of BGP multipath, generally the decision of using multiple path to deliver the traffic isperformed inside the autonomous system by an iBGP according to multiple criteria excluding the eBGP linkbandwidth.

BGP linkbw advertise bandwidth of an autonomous system exit link as extended community to iBGP.

Some requirements are to be considered:

Only between directly connected eBGP peers. BGP extended community should be enabled between iBGP. CEF should be enabled everywhere.

Figure 1 illustrates the lab topology used to implement BGP linkbw

Figure1: Topology



Inside AS 64540, R1, R2 and R3 establish full mesh iBGP sessions, the same for AS 64550: R4, R5, R6and R7 establish full mesh iBGP sessions.

Links R2R4, R5R3, R6R3 are direct eBGP sessions using interfaces ip addresses as sources anddestinations.

Network default behavior

The network default configuration is as follow:

AS 64540:

R1:

R1(configrouter)#do sh ip bgpBGP table version is 3, local router ID is 10.10.10.1Status codes: s suppressed, d damped, h history, * valid, > best, i –internal, r RIBfailure, S StaleOrigin codes: i – IGP, e – EGP, ? – incomplete Network Next Hop Metric LocPrf Weight Path*> 10.10.10.0/24 0.0.0.0 0 32768 i* i70.70.70.0/24 3.3.3.3 0 100 0 64550 i*>i 2.2.2.2 0 100 0 64550 iR1(configrouter)#

R1(configrouter)#do sh ip bgp 70.70.70.0BGP routing table entry for 70.70.70.0/24, version 3Paths: (2 available, best #2, table DefaultIPRoutingTable) Not advertised to any peer 64550 3.3.3.3 (metric 2297856) from 3.3.3.3 (3.3.3.3) Origin IGP, metric 0, localpref 100, valid, internal 64550 2.2.2.2 (metric 2297856) from 2.2.2.2 (2.2.2.2) Origin IGP, metric 0, localpref 100, valid, internal, bestR1(configrouter)#

the default path chosen is through R2R4:

R1(configrouter)#do traceroute 70.70.70.1 source 10.10.10.1 Type escape sequence to abort.Tracing the route to 70.70.70.1 1 192.168.12.2 24 msec 320 msec 452 msec 2 192.168.24.2 1004 msec 716 msec 484 msec 3 192.168.47.2 292 msec * 556 msecR1(configrouter)#

So the traffic from R1 to R7 takes the path R1R2R7

Table1: best path selection for 70.70.70.1/24 from R1

Attribute Path1 Path21 weight 0 02 local preference 100 100



3 originated locally No No4 AS_PATH 64550 645505 ORIGIN i i6 MED 0 07 eBGP<>iBGP iBGP iBGP8 Best IGP metric to NEXTHOP 2297856 22978569 Multipath No No10 oldest path No No11 Lowest neighbor routerID 3.3.3.3 2.2.2.2 <<<

AS 64550:

R7:

R7(configrouter)#do sh ip bgpBGP table version is 3, local router ID is 70.70.70.1Status codes: s suppressed, d damped, h history, * valid, > best, i –internal, r RIBfailure, S StaleOrigin codes: i – IGP, e – EGP, ? – incomplete Network Next Hop Metric LocPrf Weight Path* i10.10.10.0/24 5.5.5.5 0 100 0 64540 i*>i 4.4.4.4 0 100 0 64540 i* i 6.6.6.6 0 100 0 64540 i*> 70.70.70.0/24 0.0.0.0 0 32768 iR7(configrouter)#

R7(configrouter)#do traceroute 10.10.10.1 source 70.70.70.1 Type escape sequence to abort.Tracing the route to 10.10.10.1 1 192.168.47.1 8 msec 268 msec 104 msec 2 192.168.24.1 164 msec 348 msec 136 msec 3 192.168.12.1 276 msec * 260 msecR7(configrouter)#

So the traffic from R7 to R1 takes the path R7R4R2R1

R7(configrouter)#do sh ip bgp 10.10.10.0BGP routing table entry for 10.10.10.0/24, version 3Paths: (3 available, best #2, table DefaultIPRoutingTable) Not advertised to any peer 64540 5.5.5.5 (metric 2297856) from 5.5.5.5 (5.5.5.5) Origin IGP, metric 0, localpref 100, valid, internal 64540 4.4.4.4 (metric 2297856) from 4.4.4.4 (4.4.4.4) Origin IGP, metric 0, localpref 100, valid, internal, best 64540 6.6.6.6 (metric 2297856) from 6.6.6.6 (6.6.6.6) Origin IGP, metric 0, localpref 100, valid, internalR7(configrouter)#

R4R2 link is chosen as the best path to reach the prefix 10.10.10.1/24:



Table2: best path selection for 10.10.10.1/24 from R7

Attribute Path1 Path2 Path3

1 weight 0 0 02 local preference 100 100 1003 originated locally No No No4 AS_PATH 64540 64540 645405 ORIGIN i i i6 MED 0 0 07 eBGP<>iBGP iBGP iBGP iBGP8 Best IGP metric to

NEXTHOP2297856 2297856 2297856

9 Multipath No No No10 oldest path No No No11 Lowest neighbor router

ID5.5.5.5 4.4.4.4 <<< 6.6.6.6

BGP LinkBW deployment

The best way to utilize BW resources is to loadshare the traffic among the three eBGP link according to theirBW:

let’s recall the requirements for using BGP link BW:

Requires BGP multipath configured.

Enable BGP ext. community between iBGP.

Enable CEF everywhere.

General configuration:

On each iBGP speaker with multilink ramification, enable iBGP multipath

router bgp <ASnbr> maximumpaths <n> maximumpaths ibgp <n>

router bgp <ASnbr> addressfamily ipv4 neighbor <iBGP_peer> activate neighbor <iBGP_peer> sendcommunity extended!iBGP peer to which extended community is to be send. neighbor <eBGP_peer> activate neighbor <eBGP_peer> dmzlinkbw!Allow eBGP bandwidth to be propagated through linkbw extended community bgp dmzlinkbw!“bgp dmzlinkbw” is configured on any router whose eBGP link bandwidth!will be used for loadbalancing. exitaddressfamily



As 65540:

R1(iBGP):

router bgp 64540 addressfamily ipv4 neighbor 2.2.2.2 activate neighbor 3.3.3.3 activate maximumpaths 3 maximumpaths ibgp 3 exitaddressfamily

eBGP speaker R2:

router bgp 64540 addressfamily ipv4 neighbor 1.1.1.1 activate neighbor 1.1.1.1 sendcommunity extended neighbor 1.1.1.1 nexthopself neighbor 3.3.3.3 activate neighbor 3.3.3.3 nexthopself neighbor 192.168.24.2 activate neighbor 192.168.24.2 dmzlinkbw bgp dmzlinkbw exitaddressfamily

eBGP speaker R3:

router bgp 64540 addressfamily ipv4 neighbor 1.1.1.1 activate neighbor 1.1.1.1 sendcommunity extended neighbor 1.1.1.1 nexthopself neighbor 2.2.2.2 activate neighbor 2.2.2.2 nexthopself neighbor 192.168.35.2 activate neighbor 192.168.35.2 dmzlinkbw neighbor 192.168.36.2 activate neighbor 192.168.36.2 dmzlinkbw maximumpaths 2 maximumpaths ibgp 2 bgp dmzlinkbw exitaddressfamily

Verification:

R1#sh ip routeCodes: C – connected, S – static, 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 i – ISIS, su – ISIS summary, L1 – ISIS level1, L2 – ISIS level2 ia – ISIS inter area, * – candidate default, U – peruser staticroute o – ODR, P – periodic downloaded static route Gateway of last resort is not set 192.168.12.0/30 is subnetted, 1 subnetsC 192.168.12.0 is directly connected, Serial1/0 1.0.0.0/32 is subnetted, 1 subnetsC 1.1.1.1 is directly connected, Loopback0 192.168.13.0/30 is subnetted, 1 subnetsC 192.168.13.0 is directly connected, Serial1/1 2.0.0.0/32 is subnetted, 1 subnetsD 2.2.2.2 [90/2297856] via 192.168.12.2, 03:20:35, Serial1/0 70.0.0.0/24 is subnetted, 1 subnetsB 70.70.70.0 [200/0] via 3.3.3.3, 01:11:12 [200/0] via 2.2.2.2, 01:11:12 3.0.0.0/32 is subnetted, 1 subnetsD 3.3.3.3 [90/2297856] via 192.168.13.2, 03:20:29, Serial1/1 10.0.0.0/24 is subnetted, 1 subnetsC 10.10.10.0 is directly connected, Loopback1R1#

R1#sh ip route 70.70.70.1Routing entry for 70.70.70.0/24 Known via “bgp 64540″, distance 200, metric 0 Tag 64550, type internal Last update from 2.2.2.2 01:08:48 ago Routing Descriptor Blocks: 3.3.3.3, from 3.3.3.3, 01:08:48 ago Route metric is 0, traffic share count is 1 AS Hops 1 Route tag 64550 * 2.2.2.2, from 2.2.2.2, 01:08:48 ago Route metric is 0, traffic share count is 1 AS Hops 1 Route tag 64550 R1#

R1:

R1#sh ip bgp 70.70.70.1BGP routing table entry for 70.70.70.0/24, version 7Paths: (2 available, best #2, table DefaultIPRoutingTable)Multipath: eBGP iBGP Not advertised to any peer 64550 3.3.3.3 (metric 2297856) from 3.3.3.3 (3.3.3.3) Origin IGP, metric 0, localpref 100, valid, internal, multipath DMZLink Bw 1443 kbytes 64550 2.2.2.2 (metric 2297856) from 2.2.2.2 (2.2.2.2) Origin IGP, metric 0, localpref 100, valid, internal, multipath, best DMZLink Bw 12500 kbytesR1#

Note the proportion of the link BW of path 2 (through 2.2.2.2) against link BW of path 1 (through 3.3.3.3).



Table3: best path selection for 70.70.70.1/24 from R1 after BGP Linkbw

Attribute Path1 Path21 weight 0 02 local preference 100 1003 originated locally No No4 AS_PATH 64550 645505 ORIGIN i i6 MED 0 07 eBGP<>iBGP iBGP iBGP8 Best IGP metric to NEXTHOP 2297856 22978569 Multipath 2 <<<< 2 <<<<10 oldest path No No11 Lowest neighbor routerID 3.3.3.3 2.2.2.2

R3:

R3#sh ip routeCodes: C – connected, S – static, 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 i – ISIS, su – ISIS summary, L1 – ISIS level1, L2 – ISIS level2 ia – ISIS inter area, * – candidate default, U – peruser staticroute o – ODR, P – periodic downloaded static route Gateway of last resort is not set 192.168.12.0/30 is subnetted, 1 subnetsD 192.168.12.0 [90/2681856] via 192.168.13.1, 03:21:04, Serial1/0 1.0.0.0/32 is subnetted, 1 subnetsD 1.1.1.1 [90/2297856] via 192.168.13.1, 03:21:04, Serial1/0 192.168.13.0/30 is subnetted, 1 subnetsC 192.168.13.0 is directly connected, Serial1/0 2.0.0.0/32 is subnetted, 1 subnetsD 2.2.2.2 [90/2809856] via 192.168.13.1, 03:21:04, Serial1/0 70.0.0.0/24 is subnetted, 1 subnetsB 70.70.70.0 [20/0] via 192.168.35.2, 01:11:47 [20/0] via 192.168.36.2, 01:11:47 3.0.0.0/32 is subnetted, 1 subnetsC 3.3.3.3 is directly connected, Loopback0 10.0.0.0/24 is subnetted, 1 subnetsB 10.10.10.0 [200/0] via 1.1.1.1, 01:18:16 192.168.36.0/30 is subnetted, 1 subnetsC 192.168.36.0 is directly connected, Serial1/1 192.168.35.0/30 is subnetted, 1 subnetsC 192.168.35.0 is directly connected, Ethernet0/0R3#

R3#sh ip route 70.70.70.1Routing entry for 70.70.70.0/24 Known via “bgp 64540″, distance 20, metric 0 Tag 64550, type external Last update from 192.168.36.2 01:09:28 ago Routing Descriptor Blocks:



* 192.168.35.2, from 192.168.35.2, 01:09:28 ago Route metric is 0, traffic share count is 1 AS Hops 1 Route tag 64550 192.168.36.2, from 192.168.36.2, 01:09:28 ago Route metric is 0, traffic share count is 1 AS Hops 1 Route tag 64550 R3#

R3#sh ip bgp 70.70.70.1BGP routing table entry for 70.70.70.0/24, version 6Paths: (3 available, best #1, table DefaultIPRoutingTable)Multipath: eBGP iBGP Advertised to updategroups: 1 2 3 64550 192.168.35.2 from 192.168.35.2 (5.5.5.5) Origin IGP, localpref 100, valid, external, multipath, best DMZLink Bw 1250 kbytes 64550 2.2.2.2 (metric 2809856) from 2.2.2.2 (2.2.2.2) Origin IGP, metric 0, localpref 100, valid, internal 64550 192.168.36.2 from 192.168.36.2 (6.6.6.6) Origin IGP, localpref 100, valid, external, multipath DMZLink Bw 193 kbytesR3#

Note the proportion of the link BW of path 1 (through 192.168.35.2) against link BW of path 1 (through192.168.36.2).

AS 64550:

The same configuration can be done for AS 64550 to have a symmetric traffic flow between the two ASs:

R4:

R4#bgpcfrouter bgp 64550 addressfamily ipv4 neighbor 5.5.5.5 activate neighbor 6.6.6.6 activate neighbor 7.7.7.7 activate neighbor 7.7.7.7 sendcommunity extended neighbor 192.168.24.1 activate neighbor 192.168.24.1 dmzlinkbw bgp dmzlinkbw exitaddressfamily

R5:

bgp 64550 addressfamily ipv4 neighbor 4.4.4.4 activate



neighbor 6.6.6.6 activate neighbor 7.7.7.7 activate neighbor 7.7.7.7 sendcommunity extended neighbor 192.168.35.1 activate neighbor 192.168.35.1 dmzlinkbw bgp dmzlinkbw exitaddressfamily

R6:

router bgp 64550 addressfamily ipv4 neighbor 4.4.4.4 activate neighbor 5.5.5.5 activate neighbor 7.7.7.7 activate neighbor 7.7.7.7 sendcommunity extended neighbor 192.168.36.1 activate neighbor 192.168.36.1 dmzlinkbw bgp dmzlinkbw exitaddressfamily

R7:

router bgp 64550 addressfamily ipv4 neighbor 4.4.4.4 activate neighbor 5.5.5.5 activate neighbor 6.6.6.6 activate maximumpaths 3 maximumpaths ibgp 3 exitaddressfamily

R7#sh ip bgp 10.10.10.1BGP routing table entry for 10.10.10.0/24, version 9Paths: (3 available, best #3, table DefaultIPRoutingTable)Multipath: eBGP iBGPFlag: 0×800 Not advertised to any peer 64540 5.5.5.5 (metric 2297856) from 5.5.5.5 (5.5.5.5) Origin IGP, metric 0, localpref 100, valid, internal, multipath DMZLink Bw 1250 kbytes 64540 6.6.6.6 (metric 2297856) from 6.6.6.6 (6.6.6.6) Origin IGP, metric 0, localpref 100, valid, internal, multipath DMZLink Bw 193 kbytes 64540 4.4.4.4 (metric 2297856) from 4.4.4.4 (4.4.4.4)



Share this:

Like this: Be the first to like this post.

Origin IGP, metric 0, localpref 100, valid, internal, multipath, best DMZLink Bw 12500 kbytesR7#

Table4: best path selection for 10.10.10.1/24 from R7 after configuring BGP linkbw

Attribute Path1 Path2 Path31 weight 0 0 02 local preference 100 100 1003 originated locally No No No4 AS_PATH 64540 64540 645405 ORIGIN i i i6 MED 0 0 07 eBGP<>iBGP iBGP iBGP iBGP8 Best IGP metric to NEXT

HOP2297856 2297856 2297856

9 Multipath 3 <<<< 3 <<<< 3 <<<<10 oldest path No No No11 Lowest neighbor routerID 5.5.5.5 4.4.4.4 6.6.6.6

CONCLUSION

BGP linkbw provides an optimal way to use link bandwidth resources between autonomous systems, makesure CEF is enabled (enabled by default), iBGP multipath is already configured and enable the propagation ofthe extended community to iBGP neighbors.

Tags: BGP, Load+Balancing

Comments (4)

4 Comments »

1.

What RFC contain the feature Load Sharing to BGPMultipath ? This is standard or not ?

Thank´s regard,

Comment by Maurício — September 16, 2011 @ 7:57 pm | Reply

Hi Maurício,It looks like there is an RFC about how to use extended community attribute for BGP Link

Print Email Facebook Digg StumbleUpon Twitter Reddit

Like



Bandwidth Extended Community

Hope it helps.AJN

Comment by cciethebeginning — September 16, 2011 @ 10:14 pm | Reply

2.

I’ve been attempting unequal cost load balancing over bgp but have run into a snag.

R3#sh ip bgp 0.0.0.0BGP routing table entry for 0.0.0.0/0, version 485Paths: (2 available, best #1, table DefaultIPRoutingTable)Multipath: eBGP iBGPNot advertised to any peer999, (received & used)10.1.1.2 (metric 130816) from 10.1.1.2 (10.1.1.2)Origin IGP, metric 0, localpref 400, valid, internal, multipath, bestDMZLink Bw 250000 kbytes888, (received & used)10.1.1.1 (metric 130816) from 10.1.1.1 (10.10.1.1)Origin IGP, metric 0, localpref 400, valid, internal, multipathDMZLink Bw 1250000 kbytes

R3#sh ip route 0.0.0.0 0.0.0.0Routing entry for 0.0.0.0/0, supernetKnown via “bgp 111″, distance 200, metric 0, candidate default pathTag 999, type internalLast update from 10.1.1.1 00:14:42 agoRouting Descriptor Blocks:10.1.1.2, from 10.1.1.2, 00:14:42 agoRoute metric is 0, traffic share count is 1AS Hops 1Route tag 999* 10.1.1.1, from 10.1.1.1, 00:14:42 agoRoute metric is 0, traffic share count is 5AS Hops 1Route tag 999

It looks good so far… BUT:

R3#sh ip cef 0.0.0.0 0.0.0.0 int0.0.0.0/0, epoch 0, RIB[B], refcount 6, perdestination sharingsources: RIB, D/N, DRHsubblocks:DefNet source: 0.0.0.0/0ifnums:GigabitEthernet0/2(134): 190.10.10.1



GigabitEthernet0/1(146): 190.10.10.5path 028518F0, path list 02848C5C, share 1/1, type recursive nexthop, for IPv4, flags resolvedrecursive via 10.1.1.2[IPv4:Default], fib 0288E290, 1 terminal fibpath 0318BAD8, path list 028471F0, share 1/1, type attached nexthop, for IPv4nexthop 190.10.10.1 GigabitEthernet0/2, adjacency IP adj out of GigabitEthernet0/2, addr190.10.10.1 02CC7940path 0318BBC0, path list 02848C5C, share 5/5, type recursive nexthop, for IPv4, flags resolvedrecursive via 10.1.1.1[IPv4:Default], fib 028998B8, 1 terminal fibpath 0318BB4C, path list 030E696C, share 1/1, type attached nexthop, for IPv4nexthop 190.10.10.5 GigabitEthernet0/1, adjacency IP adj out of GigabitEthernet0/1, addr190.10.10.5 02CC44C0output chain:loadinfo 028347D4, persession, 2 choices, flags 0003, 5 locksflags: Persession, forrxIPv416 hash bucketsIP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0IP adj out of GigabitEthernet0/2, addr 190.10.10.1 02CC7940IP adj out of GigabitEthernet0/1, addr 190.10.10.5 02CC44C0Subblocks:None

The routing table shows traffic share ratio of 5:1, but the CEF table still shows 1:1 traffic sharing. Theend result is the router does not perform unequal load balancing.

Topology is:

ISP1 ISP2| |eBGP eBGP| |R1 – R2| |iBGP iBGP\ /R3

Comment by Jon — October 30, 2011 @ 8:15 pm | Reply



Fill in your details below or click an icon to log in:

Notify me of followup comments via email.

Notify me of new posts via email.

Post CommentPost Comment

3.

wow this site is lovely i like he comments

Comment by divine — December 27, 2011 @ 7:18 am | Reply

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Categories

Select Category

Search

Recent Posts

Enter your comment here...

Email (required) (Address never made public)

Name (required)

Website



DHCPv6 fake attackStateful DHCPv6 Prefix delegation (Rapidcommit) [4/4]Stateful DHCPv6 Relay (Rapidcommit) [3/4]Stateless DHCPv6 + SLAAC [2/4]IOS DHCPv6 deployment schemes

Tags

6to4 802.1q ACL AutoRP BGP BGP attribute BSR CBAC CGMP DHCPv6 DMVPN eBGP

EIGRP Frame Relay GLBP GRE HSRP iBGP IGMP IPSec IPv6 Load BalancingmGRE Multicast NAT NBMA NHRP normalcommit NVI OSPF Path selectionPIM PIMSparse mode Policing QoS rapidcommit redistribution relay RendezvousPoint RP shared path Source path T ree troubleshooting VRFlite VRRP

Email Subscription

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Join 74 other followers

Sign me up!

Meta

RegisterLog inEntries RSSComments RSSWordPress.com

Pages

About



January 2009M T W T F S S

« Dec Feb »

1 2 3 45 6 7 8 9 10 1112 13 14 15 16 17 1819 20 21 22 23 24 2526 27 28 29 30 31

Archives

January 2012December 2011October 2011September 2011July 2011April 2011February 2011November 2010July 2010June 2010March 2010January 2010



November 2009July 2009February 2009January 2009December 2008November 2008October 2008September 2008August 2008July 2008June 2008May 2008April 2008March 2008

Spam Blocked

14,022spam comments

Theme: Rubric. Blog at WordPress.com.

BGP link-bw & multipath Load Balancing « CCIE, the beginning!

Documents

Transcript of BGP link-bw & multipath Load Balancing « CCIE, the beginning!