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Cisco Offset-List Command• Posted on Ju! "#$ %#"&

•  '! Rene (oenaar  

• in CCNP ROUTE$ Cisco$ RIP)hen !ou run a routin* +rotoco i,e EIRP or O.P/ !ou can infuence the metric of the routin* +rotoco '! chan*in* the

 'and0idth 1O.P/ or EIRP2 or '! chan*in* the dea! 1EIRP23 RIP uses ho+ count so !ou need to add some e4tra routers in

 'et0een to increase the ho+ count3

Instead of chan*in* these +arameters to infuence !our routin*$ !ou can aso use an offset-list3

The offset-ist ets !ou increase the metric 0hen !ou send a routin* u+date to !our nei*h'or or 0hen !ou receive it3

You can use this for RIP or EIRP$ it is not su++orted for O.P/3

Let me sho0 !ou an e4am+e to see 0hat I mean:

)e ha5e t0o routers runnin* RIP 5ersion %3 The router on the eft 1R"2 has t0o oo+'ac, interfaces that ha5e 'een ad5ertised in

RIP3 Here6s 0hat the routin* ta'e of R% oo,s i,e:

R2#show ip route rip Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP  D - EIGRP, EX - EIGRP extenal, ! - !SP", I - !SP" inte aea

$% - !SP" $SS extenal t&'e %, $2 - !SP" $SS extenal t&'e 2  E% - !SP" extenal t&'e %, E2 - !SP" extenal t&'e 2  i - IS-IS, s( - IS-IS s(mma&, L% - IS-IS le)el-%, L2 - IS-IS le)el-2  ia - IS-IS inte aea, * - candidate de+a(lt, - 'e-(se static o(te  o - !DR, P - 'eiodic donloaded static o(te, . - $.RP, l - LISP  / - e'licated o(te, 0 - next 1o' o)eide

Gatea& o+ last esot is not set

  %333425 is s(bnetted, % s(bnets

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R %%%3 6%234%7 )ia %82%9%2%, 33:33:%;, "astEt1enet343  %%333425 is s(bnetted, % s(bnetsR %%%%%%3 6%234%7 )ia %82%9%2%, 33:33:%;, "astEt1enet343

 Nothin* s+ecia here$ 0e see the t0o +refi4es 0ith a ho+ count of "3 Let6s increase the ho+ count of the first +refi4 '! usin* an

out'ound offset-ist on R":

R%<con+i=>#router ripR%<con+i=-o(te>#offset-list ? ?3-88@ ccess list o+ netoAs to a''l& o++set <3 selects all netoAs>

  ?%33-%888@ ccess list o+ netoAs to a''l& o++set <ex'anded an=e>  !RD ccess-list name

You need to enter the routin* +rotoco confi*uration and use the offset-ist command3 I can choose 'et0een a net0or,s or use astandard access-ist to ma,e a seection3 Let6s use an 7CL:

R%<con+i=-o(te>#offset-list 1 ?  in Pe+om o++set on incomin= ('dates  o(t Pe+om o++set on o(t=oin= ('dates

Once !ou +ic, the access-ist !ou ha5e to decide 0hether the offset-ist is in- or out'ound3 I6 use out'ound so that R% recei5es ahi*her ho+ count from R"3 The ast o+tion ets !ou set the metric:

R%<con+i=-o(te>#offset-list 1 out ?  ?3-%9@ !++set

)hen !ou use RIP 0e don6t ha5e a ot of choice3 Let6s tr! a ho+ count of 8:

R%<con+i=-o(te>#offset-list 1 out 5

Last 'ut not east$ don6t for*et to create the access-ist or the offset-ist 0i a++! to a +refi4es:

R%<con+i=>#access-list 1 permit 1.1.1.0 0.0.0.255

Here6s the resut:

R2#show ip route rip Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP  D - EIGRP, EX - EIGRP extenal, ! - !SP", I - !SP" inte aea

$% - !SP" $SS extenal t&'e %, $2 - !SP" $SS extenal t&'e 2  E% - !SP" extenal t&'e %, E2 - !SP" extenal t&'e 2  i - IS-IS, s( - IS-IS s(mma&, L% - IS-IS le)el-%, L2 - IS-IS le)el-2  ia - IS-IS inte aea, * - candidate de+a(lt, - 'e-(se static o(te

  o - !DR, P - 'eiodic donloaded static o(te, . - $.RP, l - LISP  / - e'licated o(te, 0 - next 1o' o)eide

Gatea& o+ last esot is not set

  %333425 is s(bnetted, % s(bnetsR %%%3 6%23497 )ia %82%9%2%, 33:33:%;, "astEt1enet343  %%333425 is s(bnetted, % s(bnetsR %%%%%%3 6%234%7 )ia %82%9%2%, 33:33:%;, "astEt1enet343

7'o5e !ou can see that +refi4 "3"3"3# 9%& has its ho+ count increase '! 8$ it6s no0 in tota3

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You ha5e no0 seen the out'ound offset-ist$ et6s tr! the in'ound one3 I6 create an access-ist on R% that increases the ho+ countof the ""3""3""3# 9%& +refi4:

R2<con+i=>#access-list 2 permit 11.11.11.0 0.0.0.255

That6s the access-ist$ and here6s the offset-ist:

R2<con+i=-o(te>#offset-list 2 in 10

It shoud increase the ho+ count of this +refi4 '! "# 0hene5er R% earns a'out this +refi4$ here6s the routin* ta'e of R%:

R2#show ip route rip *(= 2% %2:5:%82%%: 0SS--C!$"IGFI: Con+i=(ed +om console b& consoleCodes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP  D - EIGRP, EX - EIGRP extenal, ! - !SP", I - !SP" inte aea

$% - !SP" $SS extenal t&'e %, $2 - !SP" $SS extenal t&'e 2  E% - !SP" extenal t&'e %, E2 - !SP" extenal t&'e 2  i - IS-IS, s( - IS-IS s(mma&, L% - IS-IS le)el-%, L2 - IS-IS le)el-2  ia - IS-IS inte aea, * - candidate de+a(lt, - 'e-(se static o(te  o - !DR, P - 'eiodic donloaded static o(te, . - $.RP, l - LISP  / - e'licated o(te, 0 - next 1o' o)eide

Gatea& o+ last esot is not set

  %333425 is s(bnetted, % s(bnetsR %%%3 6%23497 )ia %82%9%2%, 33:33:29, "astEt1enet343  %%333425 is s(bnetted, % s(bnetsR %%%%%%3 6%234%%7 )ia %82%9%2%, 33:33:29, "astEt1enet343

reat; You can see that the tota ho+ count is no0 ""3

There6s one more itte thin* I6d i,e to share a'out the offset-ist3 <! defaut the offset-ist 0i 'e a++ied to a interfaces$ if !ou

on! 0ant to infuence the metric of routin* u+dates that !ou recei5e from a +articuar interface then !ou need to s+ecif! this3

Here6s ho0:

R2<con+i=-o(te>#offset-list 2 in 10 ?  s&nc s&nc inte+ace  (to-em'late (to-em'late inte+ace  BHI Bid=e-Go(' Hit(al Inte+ace  CDM-Ix CDM Ix inte+ace  C(nnel C(nnel inte+ace  Diale Diale inte+ace  "astEt1enet "astEt1enet IEEE 32  6o(t'(t omitted7

)hen !ou confi*ure the offset-ist !ou can s+ecif! the interface after the metric$ here6s an e4am+e:

R2<con+i=-o(te>#offset-list 2 in 10 FastEthernet 0/0

This tes the router on! to increase the metric for routin* u+dates that 0e recei5e on the /astEthernet #9# interface3

That6s it$ that6s a I ha5e to share a'out the offset-ist3 I ho+e this has 'een he+fu$ if !ou ha5e an! =uestions>fee free to ea5e a

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