Sunday, 17 March 2013

BGP SUMMARY CONFIGURATION

We will be talking about bgp summary configuration (as-set, advertise-map,suppresss-map,unsuppress-map). All credit here goes to Jarek (http://hackingcisco.blogspot.com). He actually made me pass my bgp exam. I will be using his topology here (but modified a little)

Like I always start, here are my default configs. Pay attention to ISP2


R1.....................
int s0/1
ip add 20.20.20.1 255.255.255.0
no shut
int  s0/0
ip add 10.10.10.1 255.255.255.0
no shut
int lo 1
ip add 150.150.150.1 255.255.255.0
no shut
exit
router bgp 100
nei 10.10.10.2 remote-as 222
nei 20.20.20.2 remote-as 200
bgp router-id 150.150.150.1
no synchronization


R2..................
int s0/0
ip add 30.30.30.2 255.255.255.0
no shut
int  s0/1
ip add 20.20.20.2 255.255.255.0
no shut
int s0/2
ip add 50.50.50.2 255.255.255.0
no shut
int lo 1
ip add 77.77.77.1 255.255.255.0
no shut
exit
router bgp 200
nei 30.30.30.1 remote-as 300
nei 20.20.20.1 remote-as 100
nei 50.50.50.1 remote-as 111
bgp router-id 77.77.77.1
no synchronization



R3..........................
int s0/0
ip add 40.40.40.1 255.255.255.0
no shut
int s0/1
ip add 30.30.30.1 255.255.255.0
no shut
int lo 1
ip add 99.99.99.1 255.255.255.0
no shut
exit
router bgp 300
nei 40.40.40.2 remote-as 222
nei 30.30.30.2 remote-as 200
bgp router-id 99.99.99.1
no synchronization



ISP1..................................
int s0/0
ip add 50.50.50.1 255.255.255.0
no shut
int lo 1
ip add 200.200.200.1 255.255.255.0
no shut
exit
router bgp 111
nei 50.50.50.2 remote-as 200
bgp router-id 200.200.200.1
no synchronization



ISP2..................
int s0/1
ip add 40.40.40.2 255.255.255.0
no shut
int  s0/0
ip add 10.10.10.2 255.255.255.0
no shut
int lo 1
ip add 100.100.100.1 255.255.255.0
no shut
int lo 3
ip add 40.0.0.1 255.255.0.0
no shut
int lo 4
ip add 40.1.0.1 255.255.0.0
no shut
int lo 5
ip add 40.2.0.1 255.255.0.0
no shut
int lo 6
ip add 40.3.0.1 255.255.0.0
no shut
int lo 7
ip add 44.4.0.1 255.255.224.0
no shut
int lo 8
ip add 44.4.32.1 255.255.224.0
no shut
int lo 9
ip add 44.4.64.1 255.255.224.0
no shut
int lo 10
ip add 44.4.96.1 255.255.224.0
no shut
exit
router bgp 222
nei 10.10.10.1 remote-as 100
nei 40.40.40.1 remote-as 300
bgp router-id 100.100.100.1
no synchronization
LETS ADD ADVERTISE THE LOOPACKS INTO BGP
exit
ip prefix-list A seq 5 permit 40.0.0.0/8 le 16
ip prefix-list B seq  5 permit 44.4.0.0/16 le 19
route-map C permit 10
match ip add prefix-list A
exit
route-map C permit 20
match ip add prefix-list B
exit
router bgp 222
redistribute connected route-map C

Now lets get down to the problems . Note that all routers in this topology would see all routes since each router is an AS only. I mean split horizon rule does not apply here

    1) Summarize all prefixes 40.x.x.x to one prefix only. Summarize prefixes  44.x.x.x but make sure that more specific prefixes are also advertised.

ISP2(conf)#router bgp 100
                     aggregate-address 40.0.0.0 255.252.0.0 summary-only
                     aggregate-address 44.4.0.0 255.255.128.0
when we do a sh ip bgp on isp2 we wld see 40.1.0.0,40.2.0.0 as being suppressed

ISP2#sh ip bgp
s> 40.1.0.0/16      0.0.0.0                  0         32768 ?
s> 40.2.0.0/16      0.0.0.0                  0         32768 ?
s> 40.3.0.0/16      0.0.0.0                  0         32768 ?

ISP1# sh ip bgp
*> 40.0.0.0/14      50.50.50.2                             0 200 300 222 I       [origin code is IGP]
*> 44.4.0.0/19      50.50.50.2                             0 200 100 222 ?

 
     2)  ISP2 is advertising the aggregate 40.0.0.0/14 .Configure ISP2 so that it also advertises more specific prefixes as follows: 40.3.0.0/16 towards R1 and 40.1.0.0/16 towards R3
On oda routers , what we have is
R1#sh ip bgp
*  40.0.0.0/14      20.20.20.2                             0 200 300 222 i
*>                  10.10.10.2               0             0 222 i
No specific routes are advertised since we applied a summary-only to our aggregate command
To solve this,
ISP2(conf)#ip prefix-list D seq 5 permit 40.3.0.0/16
                     ip prefix-list E seq 5 permit 40.1.0.0/16
                    route-map F permit 10
                    match ip add prefix-list D
                    exit
                   route-map G permit 10
                    match ip add pefix-list E
                   exit
                   router bgp 222
                  nei  10.10.10.1 unsuppress-map F
                  nei  40.40.40.1 unsuppress-map G

Dats all. Now lets go to confirm what we av just done.
R1# sh ip bgp
*  40.0.0.0/14      20.20.20.2                             0 200 300 222 i
*>                  10.10.10.2               0             0 222 i
*> 40.1.0.0/16      20.20.20.2                             0 200 300 222 ?
*> 40.3.0.0/16      10.10.10.2               0             0 222 ?
Note that we see 40.1.0.0 only because R2 is advertising it to us and the unsuppressed routes appear as incomplete

R3#sh ip bgp
*> 40.0.0.0/14      40.40.40.2               0             0 222 i
*> 40.1.0.0/16      40.40.40.2               0             0 222 ?
*> 40.3.0.0/16      30.30.30.2                             0 200 100 222 ?
Similarly we see only 40.3.0.0 bcos R2 is advertising it to us and the unsuppressed routes appear as incomplete

3)     ISP2 aggregates 44.4.0.0/19 subnet to 44.4.0.0/17 but allows more  specific ones to be advertised too. Configure ISP2 to advertise only  the aggregate route 44.4.0.0/17 except 44.4.64.0/19.

We need to remove the aggregate –address formerly configured, but first lets configure our route-map
ISP2(conf)#ip prefix-list  H seq 5 permit 44.4.0.0/19
                      ip prefix-list  H seq 10 permit 44.4.30.0/19
                      ip prefix-list  H seq 15 permit 44.4.64.0/19
                      route-map I permit 10
                      match ip add prefix-list H
                         exit
                          router bgp 222
                         no aggregate-address 44.4.0.0 255.255.128.0
                         aggregate-address 44.4.0.0 255.255.128.0 summary-only suppress-map I

To view the changes made
                        R1#sh ip bgp
*> 40.0.0.0/14      10.10.10.2               0             0 222 i
*> 44.4.0.0/17      10.10.10.2               0             0 222 i
*> 44.4.64.0/19     10.10.10.2               0             0 222 ?

4)   Remove the aggregate-command on ISP2
Configure R1 and R3 aggregation for the prefixes advertised on isp2 . Make sure that isp1 can see the all AS numbers to reach these two aggregates.

ISP2(conf-router)#no aggregate-address 44.4.0.0 255.255.128.0 summary-only suppress-map I
                              no aggregate-address 40.0.0.0 255.252.0.0 summary-only
R1(conf)#router bgp 100
                   aggregate-address 44.4.0.0 255.255.128.0 summary-only as-set
                   aggregate-address 40.0.0.0 255.252.0.0 summary-only as-set
R3(conf)#router bgp 300
                   aggregate-address 44.4.0.0 255.255.128.0 summary-only as-set
                   aggregate-address 40.0.0.0 255.252.0.0 summary-only as-set

To check the effect of these commands,
R2#sh ip bgp
   Network          Next Hop            Metric LocPrf Weight Path
*  40.0.0.0/14      30.30.30.1               0             0 300 222 ?   [origin code is incomplete]
*>                  20.20.20.1               0             0 100 222 ?
*  44.4.0.0/17      30.30.30.1               0             0 300 222 ?
*>                  20.20.20.1               0             0 100 222 ?


5)  Remove aggregate cmd in R1 and R3
Cfg R2 such that it aggregates the 40.x.x.x and 44.4.x.x but they must appear as IGP to ISP1
R1(conf)#router bgp 100
                   no aggregate-address 44.4.0.0 255.255.128.0 summary-only as-set
                   no  aggregate-address 40.0.0.0 255.252.0.0 summary-only as-set
R3(conf)#router bgp 300
                   no aggregate-address 44.4.0.0 255.255.128.0 summary-only as-set
                   no aggregate-address 40.0.0.0 255.252.0.0 summary-only as-set
Now lets get started
R2(conf)#route-map J permit 10
                   set origin igp
                    exit
                   router bgp 300
                    aggregate-address 44.4.0.0 255.255.128.0 summary-only as-set attribute-map J
                    aggregate-address 40.0.0.0 255.252.0.0 summary-only as-set attribute-map J

                    Now lets verify our results
ISP1#sh ip bgp
> 40.0.0.0/14      50.50.50.2               0             0 200 100 222 i
*> 44.4.0.0/17      50.50.50.2               0             0 200 100 222 i

The ideal is you should be able to copy and paste all these configs into ur console
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Saturday, 16 March 2013

HITTING BGP TIMERS (HOLD-TIME, SCAN TIME, UPDATE-TIME)



HITTING BGP TIMERS (HOLD-TIME, SCAN TIME, UPDATE-TIME)

Range of AS 1 -65535 [public uses 1-64511] [private uses 64512-65535]
Default keep-alive is 60s and Holdtime is 180s
Default update(advertisement) is 5s(ibgp) and 30s(EBGP)
Default bgp scan time is 60s
We need BGP if we need to connect to more than 1 service provider or we are a transit AS
Assuming bgp has already been configured, I would only point out some key points. These are my default configs
r1
int s0/0
ip add 10.1.13.1 255.255.255.0
no shut
int f0/0
ip add 192.168.1.1 255.255.255.0
no shut
int lo 0
ip add 1.1.1.1 255.255.255.255
no shut
exit
router ospf 1
network 10.1.13.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
network 1.1.1.1 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0


r2
int s0/0
ip add 10.1.12.1 255.255.255.0
no shut
int f0/0
ip add 192.168.2.1 255.255.255.0
no shut
int lo 0
ip add 2.2.2.2 255.255.255.255
no shut
exit
router ospf 1
network 10.1.12.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0
network 2.2.2.2 0.0.0.0 area 0
exit
router bgp 100
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0



r3
int s0/1
ip add 10.1.12.2 255.255.255.0
no shut
int s0/0
ip add 10.1.13.2 255.255.255.0
no shut
int f0/0
ip add 10.1.10.2 255.255.255.0
no shut
int lo 0
ip add 3.3.3.3 255.255.255.255
no shut
exit
router ospf 1
network 10.1.13.0 0.0.0.255 area 0
network 10.1.12.0 0.0.0.255 area 0
network 3.3.3.3 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0



r4
int f0/0
ip add 192.168.1.2 255.255.255.0
no shut
int f0/1
ip add 192.168.2.2 255.255.255.0
no shut
int lo 0
ip add 4.4.4.4 255.255.255.255
no shut
exit
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0
network 4.4.4.4 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0


Now lets get to the problems.


 1)   Cfg timers on R3 to use hold timer of 21seconds
R3(config)#router bgp 100
                    #timers bgp 7 21      {that’s it}
Now how to we view our changes.
R3#clear ip bgp * [dont  do this in a production network]
R3#sh ip bgp nei  1.1.1.1
Configured hold time is 21,keepalive interval is 7 seconds, Minimum holdtime from neighbor is 0 seconds
R1#sh ip bgp nei 3.3.3.3
hold time is 21, keepalive interval is 7 seconds
This takes into the assumption that R1 was configured with the default values




        2)      Lets configure R1 to use a hold time of 90s.Remember Routers will use the lower hold-time
R1(conf)#router bgp 100
              #timers bgp 30 90
             #do clear ip bgp *
R1#sh ip bgp nei 3.3.3.3
Last read 00:00:03, last write 00:00:03, hold time is 21, keepalive interval is 7 seconds
  Configured hold time is 90, keepalive interval is 30 seconds, Minimum holdtime from neighbor is 0 seconds



3)      Change the scan time on R3 to 50s
R3(conf)#router bgp 100
              #bgp scan-time 50
To verify,
R3#sh ip bgp summary
BGP activity 4/3 prefixes, 4/3 paths, scan interval 50 secs



4)       Cfg R3 such that it send adverts(updates) to R1 very 3s
R3(conf)#router bgp 100
               #nei 1.1.1.1 advertisement-interval 3
              #do clear ip bgp *
To view changes made
#sh ip bgp nei 1.1.1.1
Scroll down to  For address family: IPv4 Unicast
Minimum time between advertisement runs is 3 seconds


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Wednesday, 13 March 2013

BASIC EIGRP ROUTING


R1
int f0/0
ip add 192.168.1.1 255.255.255.0
no shut
speed 100
duplex full
int s0/0
ip add 68.110.171.97 255.255.255.224
no shut

R2
int f0/0
ip add 192.168.1.2 255.255.255.0
no shut
speed 100
duplex full
int s0/0
ip add 192.168.2.2 255.255.255.0
no shut
int f0/0.10
encapsulation dot1q 10
ip add 192.168.10.1 255.255.255.0
no shut
int f0/0.20
encapsulation dot1q 20
ip add 192.168.20.1 255.255.255.0
no shut

R3
int s0/0
ip add 192.168.2.1 255.255.255.0
no shut
int f0/0
ip add 192.168.3.1 255.255.255.0
no shut
speed 100
duplex full
int lo 0
ip add 172.16.0.1 255.255.255.0
no shut
int lo 1
ip add 172.16.1.1 255.255.255.0
no shut
int lo 2
ip add 172.16.2.1 255.255.255.0
no shut
int lo 3
ip add 172.16.3.1 255.255.255.0
no shut
int lo 4
ip add 172.16.4.1 255.255.255.0
no shut
int lo 5
ip add 172.16.5.1 255.255.255.0
no shut
int lo 6
ip add 172.16.6.1 255.255.255.0
no shut
int lo 7
ip add 172.16.7.1 255.255.255.0
no shut

ISP
int s0/0
ip add 68.110.171.98 255.255.255.224
no shut
int lo 0
ip add 1.1.1.1 255.255.255.255
no shut


S1
int vlan 1
ip add 192.168.1.11 255.255.255.0
no shut
exit
int range f0/0 - 2
switchport trunk encapsulation dot1q
switchport mode trunk

S2
int vlan 1
ip add 192.168.1.12 255.255.255.0
no shut
exit
int f1/0
switchport trunk encapsulation dot1q
switchport mode trunk
int range f1/1 - 2
switchport mode access


S3
int vlan 1
ip add 192.168.1.13 255.255.255.0
no shut
exit
int range f2/0 - 1
switchport trunk encapsulation dot1q
switchport mode trunk
int f2/2
switchport mode access

We cfged vlans 10 and vlan 20 in vlan databse mode which I wouldn’t show

WE WOULD ASSUME THAT IP ADDRESSES, VLANS, VLAN-ROUTING(ROUTER ON A STICK) HAVE BEEN CONFIGURED.
TASKS
1   1)       Configure eigrp  so that R1,R2 and R3 can communicate
R1(conf)#router eigrp 1                                                                                                R3(conf)# router eigrp 1
                ##network 192.168.1.0 0.0.0.255                                               network 172.16.0.0 0.0.7.255
                                                                                                                                network 192.168.2.0 0.0.0.255
                                                                                                                                network 192.168.3.0 0.0.0.255
R2(conf)# router eigrp 1
                #network 192.168.10.0 0.0.0.255
 #network 192.168.20.0 0.0.0.255

2  2)      cfg s2 f1/1 as vlan 10 and let it ping all ip addresses in the network
S2(conf)# int f1/1
#switchport mode access
#switchport access vlan 10
PINGS FROM C5 TO 192.168.10.1 & 192.168.20.1 WOULD BE SUCCESSFUL.
FOR C5 TO BE ABLE TO REACH 192.168.1.0,192.168.2.0, WE WLD NEED TO CONFIGURE
R2(conf)# router eigrp 1
                #network 192.168.1.0 0.0.0.255
 #network 192.168.2.0 0.0.0.255

3   3)      tune eigrp so sat it doesnt summarize thr routes
lets do a sh ip route on R2
R2#sh ip route
D    172.16.0.0/16 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0 [filtering out only 172.16.0.0 network]
We see that eigrp automatically summarizes this network because it notices it is a discontigous network [a class B ntwk unlike 192.168.X.0 ntwk]. To fix this issue
R3(conf t)#router eigrp 1
                 #no auto-summary
R2#sh ip route
172.16.0.0/24 is subnetted, 8 subnets
D       172.16.4.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.5.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.6.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.7.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.0.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.1.0 [90/2297856] via 192.168.2.1, 00:00:07, Serial0/0
D       172.16.2.0 [90/2297856] via 192.168.2.1, 00:00:09, Serial0/0
D       172.16.3.0 [90/2297856] via 192.168.2.1, 00:00:09, Serial0/0

4   4)      summarize the lo back using the best possible summary
Note that auto-summarization wld summarize to 172.16.0.0/16. This is not the best summary.it shld be 172.16.0.0/21. Neva mind , we would talk about this later.Take note tha eigrp summary is done on the interface.
R3(conf)#int s0/0
                # ip summary-address eigrp 1 172.16.0.0 255.255.248.0
R2#sh ip route
Gateway of last resort is not set
   172.16.0.0/21 is subnetted, 1 subnets
D       172.16.0.0 [90/2297856] via 192.168.2.1, 00:00:10, Serial0/0


THANK YOU VERY MUCH!!! I HAVE BEEN AWAY FOR QUITE A WHILE. I ACTUALLY WORK IN A LAYER 2 COMPANY NAU. THEY BASICALLY SELL FIBER LINKS TO SERVICE PROVIDERS. HOPEFULLY I GET A CORE IP BASED COMPANY SOON.
I WILL UPDATE THIS MORE OFTEN NOW
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