BGP Notes
From Global Knowledge Class
1-Aug-2005
Barry Gursky
- Inaccessible next hop
- Synchronized IBGP
- Weight (highest) – local only – routemap or neighbor set – default is 0
- Local pref (highest) – local AS advertise to others – IBGP, IEBGP in rec
- Rtr Originated
- AS path (shortest)
- Origin code (lowest (IGP < EGP < incomplete (?)), network command is IGP, redistrib is ?)
- MED – MultiExit Discriminator (multi link to same AS) (lowest – Cisco default 0 – make sure you set in mixed environment)
- EBGP paths over IBGP
- If IBGP, Closest IGP neighbor path (closest based on IGP metric)
- If EBGP, prefer Oldest (most stable) path
- Router-ID (lowest BGP Router-ID)
Mandatory Well-Known Attributes
Origin (IGP, EGP, ?-redistributed)
AS-path (sequence of AS numbers)
Next-hop* (IP addr of rte to which rec rtr should forward packets toward dest)
Discretionary Well-Known Attributes
Local pref (used for consistent routing policy within AS)
Atomic aggregate (informs neighbor AS that originating rtr aggregated routes, you are summarizing your own routes)
Optional Attributes (non transitive)
MED (Multi-exit discriminator – discriminate betw multi entry points to single AS)
Optional Attributes (transitive)
Aggregator (specifies IP addr and AS # of rtr that performed route aggregation
Community (num val attached to routes as they pass a spec point in net)
*Next-Hop – set to IP addr of sending EBGP rtr unless in same (broadcast) subnet
Rtr-A
Router BGP 400
neighbor ip-address description
neighbor ip-address shutdown (temporarily disable BGP neighbor, limit re-neighboring, table reloads, etc…less penalty from neighbor router)
neighbor 11.1.1.1 remote-as 100 (AS# makes it an EBGP neighbor) (used to qualify connection)
neighbor 200.200.0.66 remote-as 400 (AS# makes it and IBGP)
neighbor 200.200.0.194 update-source Lo0 (do this to make sure src addr matches up with other neighbor statements, likely use loopback addr, make sure internal routes already exist for loopbacks)
neighbor 200.200.0.194 password cisco (md5 hash password)
neighbor 200.20.0.193 remote-as 400 (IBGP)
neighbor
200.200.0.193 update source Lo0
network 200.200.0.0 mask 255.255.255.192 (moves from routing table into BGP advertising if entries match routing table – make sure in routing table, origin code I (ISP)).
network 200.200.1.0 (uses default (classful) mask) - Remember
no autosummary (if you don’t own all subnets in particular class subnet)
aggregate-address 200.200.0.0 255.255.254.0 summary only (creates summary address, summary only suppresses specific routes, you can summarize anything in your routing table, even if you didn’t connect, network command(s) have to exist for detail under summary)
no synch – turn off after sure that you’ve fully meshed…allows you to use/advertise route even if you don’t know the route via IGP…leave synch on if you re-distribute into IGPs
neighbor shutdown (get syntax right, temporarily shuts down neighbor without deleting commands)
OR (coming from IGP)
redistribute OSPF 1 (puts all OSPF 1 routes into BGP, origin code ?, ISP origin is taken over this one))
aggregate-address 200.200.0.0 255.255.254.0
OR (if you have route to null0)
network 200.200.0.0
mask 255.255.254.0
no autosummary
ip route 200.200.0.0 255.255.254.0 null0 (static route, higher value in routing table)
neighbor 172.31.4.3 filter-list 1 out (filter AS (routes) being sent to 172.31.4.3)
ip as-path access-list 1 permit ^$ (empty AS path i.e. Networks originating in local AS)
neighbor 172.31.4.3 filter-list 2 in (filter AS (routes) being received from 172.31.4.3)
ip as-path
access-list 2 deny
neighbor 11.1.1.1
prefix-list notransit out
ip prefix-list notransit permit 200.200.0.0/23 ge 24
Weight
neighbor 11.1.1.1
route-map blahfilter in
route-map blahfilter permit 10 (route-maps used for complex filtering or setting attribute)
match ip addr prefix-list defonly
match as-path 10
set weight 100
route-map blahfilter permit 20 (or this)
match ip address prefix-list defonly
set weight 100 (and this)
Local Pref
bgp default
local-preference 60 (only iBGP rtrs not EBGP, normal default is 100)
ip as-path
access-list 10 permit _387$
ip prefix-list
defonly seq 10 permit 0.0.0.0/0
neighbor 1.2.3.4
route-map L2M in
route-map L2M permit
10
set local-preference 2000
Prepend
route-map name permit sequence match condition
neighbor address route-map
name out
MED (Multi-Exit Discriminator)
default-metric number (lower is preferred if from same AS, cisco default is 0, MEDs get passed throughout neighbor AS that you send it to)
route-map MED
set metric 100
neighbor ip-addr route-map name in | out
maybe …
bgp always-compare-med (put this everywhere in AS if you use, ignore AS src)
bgp bestpath med missing-as-worst (push to 65336
bgp deterministic-med (re-sorts routes by AS, and will choose (one of) best sent))
can be set going out, or get’s stripped going out.
shows up as metric in ‘show…’ commands
Communities
route-map name
match condition
set community value [value … ] [additive]
neighbor ip-address route-map map in | out
redistribute protocol route-map map
router bgp 213
neightbor 1.2.3.4 remote-as 387
neighbor 1.2.3.4 route-map setcomm out
neighbor 1.2.3.4 send-community
route-map setcomm
permit 10
set community 387:17
Don’t forget special communities for how do distribution within neighbor AS
neighbor ip-address default-originate Which way is this?
neighbor ip-address remove-private-as
maximum-paths number
(default, up to 6, …2 or higher, EBGP load balancing, stop processing once you
get to EBGP in path selection process (EBGP over IBGP)
if peering with loopback of EBGP
neighbor ip-address ebgp-multihop (TTL ] (default is 255, but DON’T USE, make sure to set directly, if didn’t set default would be 1 , i.e. neighbors must all be directly connected and don’t use loopback
neighbor ip-address local-as private-as (translates to a separate AS, i.e. if you’re waiting for real AS going to a 2nd ISP
bgp cluster-id cluster-id
neighbor ip-address route-reflector-client (configs an IBGP neighbor to be a client of this reflector)
neighbor group-name
peer-group
neighbor ip-address any-BGP-parameter
Good enterprise settings to do
Limit # of prefixes received from internet routers (do you really need 160,000, do you have memory or CPU do deal with them, just get default route, and maybe their local stuff from their AS)
3 different ways to get routes into IBGP
network
redistribute
route to null0 & redistribute
clear ip bgp {* | ip-address | peer-group-name} (hard bounce of neighbor connection – don’t do unless you have to)
neighbor ip-address soft-reconfiguration inbound (stores all routes received from neighbor as extra copy in memory (before any filtering is applied))
clear ip bgp ip-address soft in (resend saved copy of the received routing info through new filters)
clear ip bgp ip-address soft out (sets table version # of neighbor to 0 and when next update interval for neighbor arrives, the local router will ‘discover’ that all routes need to be sent to neighbor because they all have a table version number higher than 0
clear ip bgp {* | ip-address | peer-group-name} in (sends a route refresh message to neighbors – this requests that all routes be resent – both routers need to support this capability – needs to be negotiated between routers when bgp session is first established)
in route-refresh
out – soft out
QOS can be based on routes
Stuck in states
IDLE
- no route – IGP not configured correctly
- TCP SYN answered with RST – far side doesn’t want to do BGP
ACTIVE -> IDLE
-> ACTIVE -> IDLE …
- AS number mismatch between BGP neighbors
ACTIVE
3 way TCP port 179 handshake being sent
make sure neighbor statements
- FW blocking TCP port 179
- FW blocking all traffic
- access list blocking
- no return route
OPENSENT -
BGP Open msg being sent (BGP Ver, rtr AS, Holdtime, rtr ID, optional params)
Peer rtr accepts params, replies with Open msg
- has to accept IP # as neighbor, and AS
- no neighbor statement in other router
- update src command missing (i.e. loopbacks not on)
negotiate holdtime vs keepalive timer (keepalive timer = lowest holdtime / 3)
OPENCONFIRM –
Rtr recieves (2nd TCP connection/Open msg) response from peer
ESTABLISHED – n/a
Rtr accepts params, sends keepalive
Lower rtr ID drops TCP connection
-
synchronization not turned off
Debugging
sh ip bgp
BGP table version is 4, local router ID is 172.216.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, I – internal
Origin codes: I – IGP, e – EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
*> 197.1.1.0 0.0.0.0 0 32768 i
*> 200.20.0.0/16 150.1.0.2 0 0 456 20 i
*> 204.56.0.0/16 150.1.0.2 0 0 456 i
(no AS path from me (IGP)…)
sh ip bgp summary
BGP table version is 8, main routing table version 8
4 network entries (8/12) using 832 bytes of memory
(Best routes/Total routes – this is a typo)
5 BGP path attribute entries using 576 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
2 received paths for inbound soft reconfig
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.0.1 4 213 80 81 8 0 0 01:15:51 2
1.1.0.3 4 387 79 81 0 0 0 00:00:15 Active
1.2.0.1 4 213 82 82 0 0 0 02:15:23 Idle
show ip bgp neighbors
show ip bgp <prefix> (prefix is route)
Security bulletin from Cisco – USE MD5
Security bulletin from Cisco – no BGP log-neigbor changes (look up on Internet…)
Uses
Designed for Policy and Scalability
ISP
Dual Homed Internet connection
MPLS
Transit selling our services
RFC1721
BGP
- only one way to go
- like spanning tree
- no loadshare
- 12 if-then choices
BGP is external Gateway Protocol
designed to run between ASes i.e. between companies
EIGRP uses AS just to build neighbors
routing updates actually don’t use AS # in EIGRP…
If you see ASes in routing update not from your domain drop it
1-64511 public assigned by ARIN, RIPE, etc…
64512-65535 private
InterNIC – APNIC, RIPE, ARIN, sub-divisions…
NAPs – 7
Private peering points…
Masks have no class
CIDR/Supernetting
IBGP – Internal – doesn’t replace IGP – used to share external information internally – running BGP internally between routers to share what’s learned external information internally. Uses Metric to evaluate best path.
EBGP – External
BGP provides routing table with best external routes
BGP calculates separately, doesn’t respond instantly
BGP doesn’t have to be physically connected…
ASPath – Looked at as hop counts…1st thing BGP looks at as how to get there…
Origin – 2nd thing BGP looks at as how to get there…
BGP doesn’t always get best path
BGP never knows bandwidth
Policy based routing protocol
Can be over-ridden
I-dump-it-on-you policy
push your bandwidth to other carriers…
BGP never fully converges
Only cares about itself – internalized per router convergence
Use more then default route advertised via BGP if you want to get to other addresses on the internet
Can accept partial updates (for only user networks I’m interested in)
Big providers need to get full updates (larger routers 128M min for 160,000, 256M recommended)
RIP spoof source dest
OSPF authentication but must be processed to see if we should pay attention
BGP unicast
Routing protocol is an application L7
TCP port 179
reliable / connection-oriented
Security
Ignore anything that’s not from a neighbor
TCP so depends an seq #s and acks
authentication – MD5 –
Can also filter what accept and what don’t
BGP uses 3 tables
- routing
- topology/BGP/FIB (holds all of table)
- neighbors
BGP only sends updates
Reliable updates
- use TCP as transport protocol port 179
- no periodic updates
- periodic keepalives to verify TCP connectivity
- Triggered updates are buatched and rate limited
- every 5 seconds for internal peer (IBGP)
- every 30 seconds for external peer (EBGP)
ISPs cannot have default route…
Chap – Est BGP Sessions
BGP neighbors are configured manually
IBGP and EBGP – same protocol but different policies
EB
IDLE – do I have a route to my neighbor,
ACTIVE – 3way hand-shake (tcp establishing)
OPENSENT
BGP OPEN msg
BGP version
AS # of local rtr
Holdtime
BGP router identifier
Optional parameters
(note no IP addr, look to L3)
OPENCONFIRM
ESTABLISHED
(now we can exchange BGP routes)
Use loopback for peering addresses. That way when new neighbor connection is changed you don’t dump the entire address table)
sh ip bgp summary
Table Version – what version of my table have I sent them.
- if yours and the one you sent are same, you’re converged…
debug ip tcp transactions
debug ip bgp events
KEEPALIVE/HOLD 20/60
Note that holdtime is in BGP OPEN msg, agree to lower hold time.
holdtime is agreed to be 3 missed keepalives (i.e. lower holdtime/3)
this only gets done at neighbor establishment
Prefix is routing entry i.e. 200.200.1.0/24
network entries – routes
path entries – potential routes
don’t forget send updates in batches, not instantaneously…
MD5 Authentication (Hash)
Make sure you peer with IBGP neighbors also
Anything you learn from IBGP neighbor can repeat to other IBGP neigbors
Anything learned from EBGP neighbor can repeat to everyone else but one learned from (split horizon)
well-known attributes must be supported by all routers
BGP network command tells what we want to take from routing table and originate in BGP world…classful by nature…if you don’t want, make sure to type mask
BGP autosummarizes automatically…summarizes to class…
next-hop attribute – best path
IBGP – don’t change next hop – to get to next hop
redistribute
connected
B 1.0.0.0/8 11.1.1.1
recursive route lookup
OSPF 11.1.1.1
OR break rool
B 1.0.0.0/8 200.200.0.192
neighbor 200.200.0.193 next-hop-self
200.
local-preference – used for consistent routing policy within AS defaults to 100
get’s entire AS to flow to system one way…
Atomic aggregate
debug ip bgp update (never use in prod rtr (too many updates – will take down router))
sh ip bgp (probably never type in prod router, too many routes)
wights
LocPrrf
Am I next hop
Shortest Path
sh ip bgp 199.220.0.0 (parse table using prefix)
or
sh ip bgp 199.220.0.0
255.255.255.192
admin distance 20 ([20/0] in route)
lower is better
EBGP is 20
IGP is 90->170
compare if exactly same
metric 0 ([20/0] in route)
BGP is always 0 because multiple BGP route selection
debug ip routing
shows any changes to routing table
tables
route table BGP/FIB neighbors
debug ip bgp update
OK to oversummarize if you own more than 50% of subnet…
(EBGP) route dampening – add points and shutdown – 3 times and you’re out ‘till you’re up for a while…
Day 2
Transit Network can’t have default routes…creates loops
In EBGP set next-hop to ourselves, if neighbor not in same subnet
in IBGP pass next-hop
IBGP sharing border/external routes,
IGP only does internal router
BGP core rtr – any router that may be involved in forwarding between routers…
BGP split-horizon
EBGP – don’t advertise back to neighbor you learned it from
IBGP – anything you learn via IBGP neighbor, don’t advertise to other EBGP neighbor
don’t forget about recursive lookup
BGP route neighbor lookup in
Synchronization Rule
- Anything learned via IBGP cannot use or re-advertise unless you already new about in your IGP.
- SAFETY RULE – Take off carefully
- no synch – already done in 12.3 (default)
Redistribution
Typically not desired. Too much lost in translation.
Recommended to maintain in iBGP and necessary stuff in IGP
Alwasys run IBGP sessions between loopback interfaces
QUEST: Research next-hop self
Edge routers usually use next-hop self
Don’t use if more then 1 hop away…
IBGP doesn’t change attributes, EBGP change it
IBGP doesn’t synch, EBGP synchs
MEDs, can’t send local pref
BATCH updates 5 secons IBGP, 30 seconds EBGP neighbor
EBGP perfered over IBGP in routes
CEF (BGP Style)– do recursive lookup before we see data and put in switch cache…
turn CEF on if it’s not on by default (Switches it is, Rtrs it isn’t)
Route once/Switch Many – Cache only holds permitted…
route-dampening – point system
Never accept routes on your own network (subnets)!
don’t change admin value on IBGP and IBGP
Filtering techniques get rid of transit network
Multihomed Cust Routing Policies
- one provider is primary; the other is backup
- traffic to direct customers of the ISPs goes direct; all other traffic goes through primary provider
- All traffic to a particular part of world goes through one ISP
- Traffic toward a specific destination goes through only on eof the ISPs.
2 types of route policy – Filtering & Route Selection
uses regular expressions
ip as-path access-list 1 permit 31
implicit deny (at the end of the access path)
Regular Expressions
| or
[ … ] ranges [1-4] [1234]
. matches any single character
^ matches begiinning of string
$ matches end of string
_ matches any delimiter (beginning, end, white space, tab, comma ‘(‘, ‘)’ )
( ) grouping smaller expressions into larger expressions
\ single-character patterns, remove pecial meaning by preceding each character with a \
* matches 0 or more characters or sets
+ matches 1 or more characters of sets
? matches 0 or 1 character or sets
_23(_79)?_45_
23 followed by 79 or or 1 times
\1
Patterns
_100_ Going through AS 100, i.e. 100 is somewhere in AS list
^100$ Directly connected to AS 100, i.e. only thing in list
_100$ Originated in AS 100, i.e. something with 100 all the way on the right
^100_. Networks behind AS100, i.e. 100 is on the left and there’s something behind it
^[0-9]+$ AS paths one AS long
^([0-9]+)(_\1)*$ Supposed to be prepending performed in neighboring originating AS but doesn’t work
^$ (empty AS path i.e. Networks originating in local AS)
.* matches everhting.
show ip
as-path-access-list [filter-list]
show ip bgp
filter-list access-list-number
show ip bgp regexp regular-expression
Confederations
IEBGEP – intra-confederation BGP
( internal – confederation lists )
(65001 65002) – gets replaced with real AS on way out to eBGP
no router bgp
as-number
router bgp member-as-number
bgp confederation identifier external-as-number
bgp confederation peers list-of-intra-confederation-as
show ip bgp neighbor
{ prefix }
show ip bgp prefix
as-set at end of path
{400,190,8224} these are some of the ASes that were summarized…
Influence return path
MEDS
Prepend multiple of same AS path (400 400 400 400)
PRACTICE show regexpressions an ASes et. al.
QUESTION: WHY NOT SEPARATE ROUTERS
Lose IGP parameters
named access lists can be have numbered lists
distribute list
access list 100 deny ip 10.0.0.0 0.255.255.255. 255.0.0.0 0.255.255.255
anything network 10.x.x.x subnet 255.x.x.x
ip prefix-list list-name
neighbor 11.1.1.1 prefix-list notransit out
ip prefix-list notransit permit 200.200.0.0/23 ge 24
IOS – t train becomes next major revision production…
Clear IP BGP tears down list and rebuilds it…
QUESTION: Can we use prefix lists with other things than BGP filter lists?
minimally to OSPF, but basically no.
prefix list is newer version of distribute list – both supported
standard – filter 1918 addresses in from external neighbor
Filters
AS-Path Filters
ip as-path access-list 1 permit ^$
Prefix filters (IP
Addresses)
neighbor 11.1.1.1 prefix-list notransit out
ip prefix-list notransit permit 200.200.0.0/23 ge 24
ORF – O Route Filter
route-maps – combine as-path filter and prefix filters OR BGP attributes
route-map policy permit 10
match ip address 1 2 (on same line 1 OR 2)
match origin IGP
set local-pref 200
route-map policy permit (default is 10 so add to 10)
match ip address prefix-list net 3 (multi lines in a row are ANDed)
match ip address prefix-list net 4
route-map policy permit 200 (no match condition means any)
access-list 1 permit 10.1.0.0
access-list 2 permit 10.2.0.0
ip prefix-list net 3 permit 10.3.0.0/16
neighbor 11.1.1.1 route-map newpolicy out
ip prefix-list net1 permit 1.0.0.0/8
ip prefix-list net1 deny 0.0.0.0/0 le 32
ip as-path access-list 2 permit _100_
ip as-path access-list 2 deny .*
route-map newpolicy deny 10
match ip address prefix-list net1
match as-path 2
route-map newpolicy deny 20
match ip address prefix-list rfe1928
route-map newpolicy permit 30
match as-path 1
set metric 100 (MED)
asdf asdf
permit permit permit
deny permit deny
permit deny no match
deny deny no match
Log statement on end of access list bypasses cacheing
Soft Outbound Reconfiguration
Soft inbound – stores dupl copy of entire table and filters off of that bad idea memory intensive
Soft In
Route Refresh – Please resend routes without tearing down neighbor connection
In
PBR – Policy Based Routing
Question: i in begin of ‘sh ip bgp’?
internal
Question: loopback not in external links?
igp focused…
If you have a direct connection between IBGP routers use serial connections IP addresses for neighbor commands,
If you don’t have a direct connection, either re-distribute routes into IGP or don’t run
IBGP between internal routers.
Tag on routes
32 bit field number
make high order 16 bits of 32 bits into AS
1732:256 – (AS:Tag or high16bits:low16bits)
by default BGP drops tags but can be configured.
Tag numbers pre-defined by standards
- no-advertise: do not advertise routes to any peer
- local-as: do not advertise routes to any EBGP peers
- no-export : do not advertise routes to real EBGP peers (i.e. confederations)
- Internet: advertise route to Internet community
Apply tag to route directly
Rtrs
default route will be tagged no-export (so won’t forward default route through us)
routemaps can reference tags
Originated redistributed IGP routes into iBGP get max weight (32768)
Influence inbound from
internet
MEDs
community with ISPs setting local preference on their side
AS-PATH prepend
default max IGP paths
maximum-paths number (default, up to 6, …2 or higher, EBGP load balancing, stop processing once you get to EBGP in path selection process (EBGP over IBGP)
(NxN-1)/2 number of BGP neighbor links
Route Reflectors
Modifies split horizon – Reflector can repeat routes to clients and other route-reflectors
cut down on duplicate replications across same physical wire.
Route Reflector –
Client
Cluster – relationship of clients to route reflector
Cluster ID
non client
bgp cluster-id cluster-id
neighbor ip-address route-reflector-client (configs an IBGP neighbor to be a client of this reflector)
don’t route-reflect to redundant route reflectors
show ip bgp neighbors
show ip bgp ipnetwork
when reflfector recieves route directly, route reflectors mesh with other route reflctors and non clients no in another cluster
when reflector doesn’t receive route directly non-reflector only allowed to reflect to clients
QUESTION: Why does PxR4 have BGP going on? Because it’s
Look up next-hop self
Improving BGP performance
Ref manual
Queuing to TCP peer connections
Deploying BGP peer groups
Enabling path MTU feature (RFC 1911 – TCP feature)
Increaseing interface input queues
Configure a smaller interval for the BGP scanner process (scan time) – not a great idea for internet (160,000 routes)
configureing a smaller advertisiment interval between BGP neighhbors – again not a great idea for Internet, also may push flapping routes
ip tcp path-mtu-discovery [age-timer {minutes | infinite}]
show ip bgp neighbors | include max data
hold-queue length in
default size is 75 packets
look at
example show interfaces hssi 0/0/0 to confirm
neighbor {ip-address | peer-group-name}
advertisement-interval seconds
show ip bgp neighbors ip-addr includes batch advertisement minimum time between advertisement runs is 30 seconds
neighbor ip-address maximum-prefix maximum [threshold] [warning-only] [restart restart-interval] (if you don’t set a restart-interval you have to reset neighbor connection (clear…)
show ip bgp neighbors ip-addr (shows
max AS thresholds
route reflectors – Peer Group s
CPU only has to build one update per peer group no neighbor
IBGP EBGP can’t be combined
neighbor group-name
peer-group
neighbor ip-address any-BGP-parameter
individual settings override peer group seetingsoverrides individual settings
neighbor Customres peer-group
neighbor Customers route-map Cust_IN in
neighbor Customers route-map Cu
show ip bgp peer-group [peer-
BGP route dampening
RFC2439
1000 points per flap, by default > 2000 points will cut out routes associated…
half life
once over high-water mark, have to get under 750 (default)
max penalty 1 hours (12000 points)
probably wouldn’t use in enterprise…
if after you go below 750 until you hit 375, then clear slate…
flap is a route flap
Example Config
router bgp 65004
no synchronization
bgp cluster-id 143
bgp log-neighbor-changes
network 10.4.0.0 mask 255.255.255.0
network 10.4.1.0 mask 255.255.255.0
network 10.4.2.0 mask 255.255.255.0
network 10.4.3.0 mask 255.255.255.0
aggregate-address 10.4.0.0 255.255.0.0
summary-only
neighbor 10.4.100.101 remote-as 65004
neighbor 10.4.100.101 update-source Loopback0
neighbor 10.4.100.101 route-reflector-client
neighbor 10.4.100.104 remote-as 65004
neighbor 10.4.100.104 update-source Loopback0
neighbor 10.4.100.104 route-reflector-client
neighbor 10.254.0.2 remote-as 64999
no auto-summary
4
router bgp 65004
no synchronization
bgp log-neighbor-changes
neighbor 10.4.100.103 remote-as 65004
neighbor 10.4.100.103 update-source Loopback0
no auto-summary
router
advertising loopback1
PREPEND to see extra ASes
when you send out loopback prepend AS
number during redistribution
version
12.2
service
timestamps debug uptime
service
timestamps log uptime
no
service password-encryption
service
udp-small-servers
service
tcp-small-servers
!
hostname
P4R4
!
!
ip
subnet-zero
ip
tcp synwait-time 5
no
ip domain-lookup
!
!
!
!
interface
Loopback0
ip address 10.4.100.104 255.255.255.255
!
interface
Loopback1
ip address 10.44.144.1 255.255.255.0
!
interface
Ethernet0
ip address 10.4.2.4 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface
Serial0
ip address 10.4.3.4 255.255.255.0
no ip route-cache
no ip mroute-cache
no fair-queue
!
interface
Serial1
no ip address
no ip route-cache
no ip mroute-cache
shutdown
!
router
rip
version 2
network 10.0.0.0
!
router
bgp 65044
no synchronization
bgp log-neighbor-changes
network 10.44.144.0 mask 255.255.255.0
neighbor 10.4.100.101 remote-as 65004
neighbor 10.4.100.101 ebgp-multihop 5
neighbor 10.4.100.101 update-source Loopback0
neighbor 10.4.100.103 remote-as 65004
neighbor 10.4.100.103 ebgp-multihop 5
neighbor 10.4.100.103 update-source Loopback0
no auto-summary
!
ip
classless
ip
http server
!
!
!
line
con 0
exec-timeout 60 0
privilege level 15
logging synchronous
line
aux 0
transport input all
line
vty 0 4
privilege level 15
no login
!
end
P4R4#