BGP - Part5

Simple BGP configuration
အရင္ဆံုးသိသင့္တာက eBGP မွာပဲျဖစ္ျဖစ္ iBGP ျဖစ္ျဖစ္ loopback interface ကိုအသံုးမ်ားၾကပါတယ္။ ဘာျဖစ္လို႔လဲဆိုေတာ့ BGP ကို redundancy (Dual neighbor relationship) အတြက္သံုးၿပီး link availability ကိုေျဖရွင္းေပးတာျဖစ္လို႔ သာမန္ interface ႏွင့္သံုးရင္ link bandwidth ႏွင့္ BGP table memory အသုံးျပဳမႈက မလိုအပ္ပဲျမင့္ေနတာေၾကာင့္ျဖစ္ပါတယ္။ ကဲ iBGP configuration စပါၿပီ.....

Common iBGP design

iBGP configuration steps
1.Defining loopback interfaces on both BGP routers
2.Configuring remote AS with other router’s loopback interface
3.Configuring “update-source”  with loopback interface
4.Fig.2 အရ loopback ေတြကို OSPF process ထဲမွာပါသံုးရပါမယ္။

On R1,  R1(config)# int lo 3
                              # ip address 1.1.1.1 255.255.255.255
                              # router ospf 1
                              # network 1.1.1.1 0.0.0.0 area 0
                              # router bgp 5800
                              # neighbor 2.2.2.2 remote-as 5800
                              # neighbor 2.2.2.2 update-source lo 3

On R2,  R2(config)# int lo 4
                              # ip address 2.2.2.2 255.255.255.255
                              # router ospf 1
                              # network 2.2.2.2 0.0.0.0 area 0
                              # router bgp 5800
                              # neighbor 1.1.1.1 remote-as 5800
                              # neighbor 1.1.1.1 update-source lo 4

Common eBGP design

eBGP configuration steps
1.Defining loopback interfaces on both BGP routers
2.Configuring remote AS (different) with other router’s loopback interface
3.Configuring “update-source”  with loopback interface
4.Loopback interfaces 2ခု reachability ရေအာင္ static route ထည့္ေပးရပါမယ္။
5.eBGP မွာ router ေတြက packet 1ခုပို႔ရင္ header မွာ TTL value ကို “1” (default) လို႔ထားၿပီးပို႔ပါတယ္။ အဓိပါယ္က destination interface ကိုေရာက္ပို႔ 1 hop (also means directly connected) ပဲရွိတာကိုေဖာ္ျပတာပါ။ အဲတာက router 2လံုးကို physical interface ႏွင့္ခ်ိတ္ဆက္ထားရင္ problem မရွိေပမယ့္ loopback ကိုသံုးတဲ့အခါ (loopback ေတြက directly connected interface မဟုတ္လို႔) multihop command ကိုသံုးရပါတယ္။

On R1, R1(config)# int lo 1
                             # ip address 1.1.1.1 255.255.255.255
                             # ip route 2.2.2.2 255.255.255.255 s0/0
                             # ip route 2.2.2.2 255.255.255.255 s0/1
                             # router bgp 5810
                             # neighbor 2.2.2.2 remote-as 6330
                             # neighbor 2.2.2.2 update-source lo 1
                             # neighbor 2.2.2.2 ebgp-multihop 2

On R2, R2(config)# int lo 2
                             # ip address 2.2.2.2 255.255.255.255
                             # ip route 1.1.1.1 255.255.255.255 s0/0
                             # ip route 1.1.1.1 255.255.255.255 s0/1
                             # router bgp 6330
                             # neighbor 1.1.1.1 remote-as 5810
                             # neighbor 1.1.1.1 update-source lo 2
                             # neighbor 1.1.1.1 ebgp-multihop 2

15/6/2011