Routing Protocol Overview ‘Aroaters primar fancion sta nove an IP paces om ane networ to afer network. router lerns bout nonatached net “wove through canguraon of tne outer through eyname Proving grooeas Dynan I routing protocols stitute network topolgyinformeton beter cuter end prove updates thou intervention when -topoigy chengein the network ecura. Design reuters hardware Limitations may etic IP routing ta state utes, es not accommodate teplogy changes very well ence burder newer engine’, depeniing on the sie of te neterk With jramic routing protocols routers try to selec the best lop-ree pate which to forward a packet ot destination IP adress Antiwar of interconnected rovers and elated systems managed under a common nebaork administration known an adamamgus ‘system (A), 01 2cvtng dana. Theletemet' composed of thousands of autonomous systems sparing the globe \ynentheexcanton of BGP, he protocoein tlie sr designed a opt mae fr rovtng with an sutanomoussystem anda noun as Intror Gateway Protocols (GPs), Exterior Gateway Prtoces (EGP) route between sutonoMoUSs}stems, BGP 1s an EGP protocol bute len sed tin an autonomous ayer I BGP exchanges rites win an autonome pete i naw =| Ieneror BGP (BGS) session. it exchenge rites between ferent atanamoun sytem, te known 389 extent’ AGP (ASG) cen Deane ecto rvtng rect, ch RP ToL WAS NN RG NI, 2a vectors the net-hop route’ I used to reach the destination: + Distance: The tance the route metre to reach the network, + Vector: The vectra the interface ar dtection teach the network. When router receives ranting information fr a neighbor, stresit ne local routing database os received, en! he SEES ca tn Gh vt Belin Fd an FFs get) set cetera eth bes pie psthe to each scrapie certnaton, When th Bert pats sre detstmine, the ae ntl nto the outing table and are adverteed to ‘each nelghtor router. Routers running stance vector protects adverte the rating information to ther neighbors from the own perspectve, modified ‘rom the original route received. Therefore, a dstance vector protocol does nothave s complete mep of the whole network: instead ts ‘dlabae reflects ta reighor router knows haw toresch the destination network and how fr the neighbor router for the det nation network The advantage of stance vector protocols thet they require lows CPU and remy and can run on low-end routers ‘An analogy commonly used to describe distance vector protecls is oad sign at an intersection indicating thatthe destination s2 rile tothe wert; dover rut ane Binal follow th information without really owing whether tre lea sherter ar better way 20 ‘the desunation or whether he sign i even correct. gure 62 Hlustr2tes how a router ung a stance vector protocol views the net- ‘work and the direction that 3 needs to goo reach the 182,168.1.0/24 sibret A distance veto protocol selects paths purely based on distance, Itdbes not account or ink speeds or ether factors. n igure 6:2, the ik betwen Rend R7 sa neva ink with aly 64 Kapa of bandh, an ll af the other inks ae 1 Gps Ethernet link, RIP does not take tis into consideration and forward traffic eros this Un, which wil rel in pocket lots when that links oversubscribed‘The fusing upete algorithm (DUAL en enhanceddatance vector algoritm tha EIGRP une to cleats the shortest path foe stinaon within nett EIGRP edertves network nfermation tts eighbera the dtance vector protocols do butt hes serve echancerent, ait tame suggests The fllowing ere some of the enhancements intriced ina thi algithm capeed © ther datane vector algorithms: EIGRP is sometimes refered te ae yi roving prfoel Keene it ha characteristic ofboth tance vector anink-tate prot clas shown nthe preceding lit EIGRP relies on more advanced metrics other then hap count (fr example, bandwith) forts bent= pith ealculations. By deft, EIGRP advertises he total path delay ad minimum bandwith fr aroute. This nfrmaton i advertised ‘out every drecton, as happens with» tance veto ruting pratcal mew, ach rater an calcite the bet pth bed on the “etornstonprovised by eect ne ghar [igure 63 stows the previous topology but now includes E\GRP's metric calculation foreach af the inks. R38 trying to forward pockets othe 182 1681024 network. If herauting domain aaed a tance vector routing protocal, # would take the BARIGRT path, which only tw hops emey rather than the path R2-RI-—R2-R7 path, whichis three haps away. But the RI—RI=R7 path cane rot support rfc ove Kops. While the RB-—-RI-R2-—RT path e lange, it provides more bandwidth and doesnot heve ax much de= lay (Secaune ofthe seilztion process on lower-apeed interfaces) ands the path selected by EIGRP.Alnk-stte demic IP rvting prota advertines the ink stale ad ink mtr or echo te conecte inks and iecty connected ravtor to every routern the network OSPF and IS are two ink-tne rutin protocalscommanly wed in enterprine and service provide networks. OSPF advertisement ar called insite advertsements (LSA) an IS-1S uses Unk state packets (LSPs) for ts ‘As arouter cee an advertisement from 2 neighbor, stores the information in aoca database called the instate database (SDB) and advertises the lnk state information ont each of ts nlghbos routers eraciy 2 it as reeled. Te nk stat information ie ‘sell flooded thoughout the ntark, wachanged, fom router to router, just asthe arginating router advertzed i. Thilo ll ‘theroutesin the network to have 2 sychenized and Getic map of te network. Lang she complete map ofthe netor, every router inthe networe than nee Dts shores path et SP) sigan cle late the bes shortest lop fee paths. The inkstate algothm then papulsts therauting table wth tis formation, ‘ust having the complete mapof the network, ink-stte protocols unaly equine more CPU and merary than datance vector prot: ‘ols but they are Less prone oroutng oepsand make beter path decors In additon in-state protcslsare equipped wit ex ‘tended capable sucha opaque LSA for OSPF and TLV ypeilensthsae) for 5 hallow them to supper: festrescomenly sed by serice providers, such 2 MPLS trafic engneerng. [Secon snout which way ete hareet sna est path tench a destination Ege 6 lusraee Row RB woud view the mete reach the 192165 .0/24 subnet. Rl ue the sae slgorthm 353 and take the dec ink oR quaker Pec arts | pethvacor prota auch ss Ge smlarto a etnce vaca prtacl the ditferenele that instead esing she etn to esemine the best nopree pth loos a vaiou BGP path arises. SOP path etnies include atonomcus system path (Pat), mult ext icrinintor (MED) og, ex hp, local preference atomic aggregate and zggegater GP pth atutbutes are ‘covered mn Chapier M1. "BGP." 9né Chapter 12, “Advanced nar” path vector protcal guarantees lop fe paths by keeping 2 record ofeach autonomeaus system thatthe routing advertisment ‘eres Any time a outer receiver n advertisement n whch t already part af the AS, Path, the advertnement eerted been ‘cepting the AS Path would effectively euttine outing oop. Figure 65 lusts he laop revemonconcet over the falling pe 1 (ASI) aertcerthe 10.1.0 [24 netwert 082 (AS2) A athe AS 20 te AS Fath cng te network aderesement 2922. 2 R advertises the 10...0/24 network oR ard ads AS 2t the AS Path ding the neo advent to Ra 3. Rd adverts the 10.1.10/24 netwotk 0 R3 and 2dds AS to the AS Path cing the network advertisement R3. {RB ayertee the 10.10/24 nerwork bc r RI and #2 afer atang AS to he AS Fath during he network aderesamet 5. Ae Rl receives the 1..10/24 network advert sement fram Rt daeards the rvte advertisment because Rl detctt AS (AS) in he AS Path 42 and cores the advertnement aa ocp 2 Sacards he 111.028 network advarssemers for Rept ‘ets 5 AS (5 2) inthe AS Path 421" and considers ta oop ton.‘ye deaning doesnot cepet the averteeent ofthe 10) 0/28 neta am Al aun some sir to ise Bat he process happen in theater rection ar well Raters to adverts the I 0/24 neta 2 2 (on Ra) and Ril adverse ‘the pref to Rl as well. RI discards the outebecause It detects AS (AS Pat and considers it oop 25 wal. ‘router dennfas the pth pacer soul tse by evaluating the peiengt hats pagramed inthe Fannin nfarston Base (Ein The F's programed tough the outing able whi ls known a he Buia lfmelin at (RB) Te RIB com posed of routes presented rom the rovtng protocol processes, Pat SletGn as tee Ma conan ‘+ rfilenots The pea Lngth represents the number of leading bray bts in the subnet mask hat aren the on postion. + Adminisatvedatance: Ainiisatve distance (AD) sarang of te trworthness ofa outing information source. router {ears about route toe destineton fom moe then one routing protect an lhe ries hve the tre pei lang, ten the AD iseompared. 1+ Metres: A mecrets unt of mean wed by 2routng protocol nthe best path calcite. The metres vary from ne routing pro= If apacket nzeds tobe forwarded, the oute chosen depends onthe prefix length, where the longest prefix Length is alnays prefered. Fer example, (28 is preferred over 25, and/26 is preferred aver /2. The flloing nan example sing Table 62 oa eferece‘Table 6-3 touting Protocol Cefault Amiistratve Distances Connected ° Static 1 EIGRP summary route 5 External BGP (eBGP) 20 EIGRP (internal) 90 OSPF no Isis us RP 0 EIGRP (external) 70 Internal BGP (IBGP) 200 Metsics The logc for selecting the best path fre routing protocl can vary. Most IPs prefer intemal lesrned routes over external routes and further prlortiz the path with the lowest met Equal. Cost Multpathing If outing protocliemtfies multple paths 2 best path and support multple path entre, the outer installs the maura num ber of pats slowed per destnsvon. Ths snown 25 eal cst multathing (ECMP) né provides load sharing aro alin. RIP, IGR?, OSPF, ond 61 ol support ECP. ECIMP provides 2 mechani to increase bandwidth arose mulisle path by sling atic equally acrozs the tink, ‘Unequal: Cost Load Balancing By default, outing protwcls install only routes with the Lowest path mets, However, EIGRP canbe configured (nt enabled by de- feu ental mulple outs wit diferent path merc. This lows for unequal cot led balancing cross rtp patho Treffic is Static Routing “Stati routes provide peste control oer outing but may crest an administrative buen a8 the number outers ane neta ments grow, Using tic rauing requires ze network banewith becne implementing manual route entries doesnot ree com munication with ther outers Unfortunately, because the router ore nt communicating, ther no network ineligence. Wink goes dawn, ater route: ll nat be suare thatthe ner path ano langr val Static routs ae etal nen + Dynamic routing protocols cennot be ued on router because ofnted ruter CPU memory + Rovies eee from dyramic outing protects ned io be superaeded ‘Stati rates canbe cari as ane of he allowing 1+ Duetly ataced static routes + Recursive slaticrovtes + Fully pected staicroterFloating Static Routing The default AD on static route 1, but a static route can be configued with an AD value of 110 255 for aspecfic toute. The ADIs set ‘one state route by appending the AD as part ofthe command structure Using a leating static route is2 common technique fr providing bacup connect fr petiaes eamed viadyramic routing pot col. flsting state route acontigued wth a7 AD higher thar that ofthe primary rte. Gecnse the AD e higher than tot of he primary toute, installed in the RIB ony wen the par oute withdrawn, Example 610 Confguring the Floating Stave Route for = IF configure terminal Enter configuration commands, one pe ne End with CNTL/Z ‘(conti prt 10.2222. 255.255 255.010.1212 10 (conti) ip route 10-2222. 255.255.255.0 Seri 10 210, ‘sample Gl Faun Table of wth lating State ste Output ote fr su Gateway 10.00.08 varabiy subnet, 5 subnets, masts 1.1.1,.0/24 i rect cnnectea igseEtheret/ 10:2,,0724 sect comectee GiabtEteret0/0 10:22.0/24is deci comected Srl /O c c 1022220724 0/0] va 10:2.12 ‘example 6-12 foutng Tobe fer there Unk Foire [acerom me 18 configure terminal Enter configuration commands, one per line, End with CNTL/2. (conta interface GigaitEthenet0/ Y(configi} shutdown if show proute Output ented Fr euty Gateway of ast resort i nt set 10,0.0.0/815 orably subnered 5 subnets. 2 masks € 1071-0724 crecttycomecte,GgebtEtrenetOt C10122.0)24i recy comet, Seval/O S$ 1022220/24 det eamectod era Example 6-13 Vern he AD forthe Flag Stae Route Routing ety for 10.22.22.0/24 Known via"static, stance 210, metic O(ennected) Routing Descriotr Bods: * eectyeomecte. va Serat/0 Rovte metre 80 tafe share coun Virtual Routing and Forwarding iewal outing and forwaring (VRF) 2 technology that eats separate virtual routes on a physical route. Router interfaces, fut Ing ables, er ormading table ore complealy olted between VRS, preventing traffic rom are VRF frm forwarting into enather RF. Al router merfaces belong to the global VAF unt hey ae specially assigned toa user-defined VRF. The global RFs identical 1 the regular outing table of non VAF routers. Ever routes VRF maintains a separate fouting table Is pssble to allow for vertzpping IP addess anges. VF creates seomentz ‘on between network interfaces, network sbineraces,IP adesze, and racting tables, Configuring VAF ens paths are clad, network secunty s nreased, and encrypting traffic on te network ot needed to matnain pracy between VAFigure 1 shows two routes to help visualize the VAF rong table concept. One ofthe routers has no VAFs congue and the other one ha ranagerent VEF instance named MGMT. This gure can be ued as aeference forthe fllowing erp. Te ereton of maltipttocl VF instance ests the slobel configuration command vt defiitin fname, Under the VRF defn= Aion submode, the command address amily {pw pw) required to spec the appropiate address family. The VRFiatance it then atocates tothe interface wh the commend ef forwarding fname under thertrfaceconiguaion submade gn cope Ret Ee EF ce ‘The allowing steps are equedto crest a VRF and sign ito an interface: Crete a multprotocl VRF routing table by ting the command ve dfaton fm, ‘tep2.nealze se srproprins ster famlybyutng te command address fam (pw ipuG). The ares farly can be Ps, IPG, bth, ‘Step 3. Ener inefece configuration aubmode and pei the interface tobe esoite withthe VRF instance by using the command Ieee ere, ‘Step 4 saci the Vi inetance tote interface arcuate by entering he command forwarding Frame indy meat ‘configuration sobrede, ‘Step. Configure an IP adres C4, 1P6,o bat) onthe interface or sbiterfce by entering ether or both af the allowing lvl eddess pada length sample 6-20 1? Acree Congguraton inthe Gal tng Tale config interface GigaitEtheret0/1 Rilconfa- ip addres 10.031 255.255255.0 i(confah interface GigabitEthornet0/2 llconfa-1 ip address 10.04.1255255.255.0 contig vet defition MGMT Rionfgne)t address Frily pe i(contgh interface GigatEtherset0)3 llconfi) et forwarding MGMT ilconfa 3 ip adress 10.031 255.285255.0 (confab interface GigabitEthernet0/4 cout ve forwarding MGMT ont ip address 10.0.4.1255255.255.0Example 6.21 Outputef the Geka outing Table | Output omitted for bret 10.0.0.0/8 evry subaeted 4 subnets, 2 mak © 10.0:20)24 dre=y connected, Gigatsttheret/1 1 1O.03:732 crcty connected, igebtthern=t/ © 10.04.0/24is recy connected, Gigabit themetO/2 100-172 i cirety connected, GnabEthemetO/2 Example 622 Ovpu of he VRF Roving Tale Ai8 show ip route wt MGMT £Outut omitted fr brewty 10.0.0.0/8 5 vanabysibnete, 4 subnets. 2 masks © 10.03.0/24xdretycomecte, Caattternet/3 L10.0.31/2 5 crcl connected, GiguitEtemetO/3 © 1010.4.0724s deetly connected, GgabuEthernetO/4 L100:4452 1 rectycomertes abt there Routing Information Protocol * RIP is a Distance vector routing protocol. = RIP enabled routers sends their complete routing table out all active interfaces every 30 secs. = RIP uses only Hop Count to determine the best route to a remote network. = RIP has a maximum of 15 hop count by default. * Itis a classful routing protocol, which means all the devices in the network should use the same subnet mask. = But RIP v2 is a classless routing protocol which uses Prefix Routing, and also sends the subnet mask information along with the route updates. = RIP uses the Bellman-Ford Distance Vector algorithm to determine the best “path” to a particular destination. RIP version 1 = Classful Routing Protocol. = Does not include the subnet mask in the routing updates. = Updates sent as broadcasts unless the neighbor command is used which sends them unicasts.RIP version 2 = Classless Routing Protocol = Includes the subnet mask in the routing updates. = Updates sent as multicasts unless the neighbor command is used which sends them as unicasts. = RIP v2 updates are sent using the multicast address 224.0.0.9 RIP V1 & V2 = RIPV2 can interoperate with RIPV1 by default: »RIPV1 routers will sent only version 1 packets. >RIPV1 routers will receive both version 1 and 2 updates. >RIPV2 routers will both send and receive only version 2 updates. >We can control the version of RIP a particular interface will “send” or “receive”. Unless RIPV2 is manually specified, a cisco will default to RIPV1 when configuring RIP. RIP Timers = Route update timer — 30 Seconds = Route invalid timer — 90 Seconds = Route flush timer — 240 Seconds Commands to Verify = Show ip interface brief = Show ip route = Show protocols = Show ip protocols = Debug ip ripEnhanced Interior Gateway RoutingProtocol * EIGRP is also a CISCO proprietary routing protocol. * EIGRP is a classless, enhanced distance-vector protocol. * EIGRP has maximum 255 hop counts. * Like IGRP, EIGRP uses the concept of an autonomous system to describe the set of contiguous routers that run the same routing protocol and share routing information. * Autonomous system number can be any value between 1 and 65,535 * EIGRP is generally classified under Hybrid protocol. * EIGRP uses multicast address of 224.0.0.10 EIGRP Tables = Neighborship table: records of information about routers with whom neighborship relationship is formed. = Topology table: It stores route advertisements of every route received from neighbor. = Routing table: stores information about currently used routes for making routing decision. EIGRP Path = EIGRP maintain two path for each destination. » Best Path — It is also called Successor » Second best path — It is also called Feasible SuccessorEIGRP Timers = Hello packets are sent - every 5 secs on high bandwidth links - every 60 secs on low bandwidth links(<1544kbps) Hold Time = 3 times of the hello interval Verifying EIGRP * Show run = Show ip route = Sh ip route eigrp = Show ip eigrp neighbor = Show ip eigrp topology