BGP and multi OSPF and RIP

Departamento de Informática
Escola de Engenharia
Universidade do Minho
_________________________________________________________________________Tecnologias e Protocolos de Rede, 2015/2016
Tecnologias e Protocolos de Rede [2015/2016]
MERSTel/MIEI MSc
Laboratory Work TP1: Routing [Part #2]
Objectives
• Development of competences in the process of configuring RIP and OSPF routing
protocols, including the redistribution of routes between these protocols.
• Development of competences in the configuration of the external routing protocol
BGP, including conditioning/filtering of BGP routes.
• Use of network level emulation tools, e.g. CORE (Common Open Research
Emulator).
• Development of research skills and self-learning capabilities for configuring internal/
external routing protocols.
Report
• All working groups are expected to prepare a report describing the tasks/configurations
made in the context of this laboratory work.
• The definition of the report structure and included contents is the responsibility of the
working groups.
• The reports will be evaluated taking into account i) the correction/technical quality of the
solutions/settings/answers/explanations made regarding the proposed tasks/challenges
and ii ) clarity/organization/quality of the submitted report.
• The reports should be submitted by the deadline set by the teacher.
____________________________________________________________________________
In the context of this work, it is expected that students perform the adequate research for the
addressed topics. The following references/links are merely illustrative and should be
complemented with other references deemed relevant.
• http://www.nrl.navy.mil/itd/ncs/products/core
• http://downloads.pf.itd.nrl.navy.mil/core/vmware-image/
• Several manuals/documentation regarding the configuration of routing protocols in
CISCO equipment can be searched on the net, with many available in
http://www.cisco.com/........
[note: In the CORE emulator the routing processes are based on the Quagga
framework (http://www.nongnu.org/quagga/). However, most of the configuration
commands are quite similar to the ones commonly used in CISCO IOSs]
____________________________________________________________________________
Tasks
- Familiarization with the emulator CORE (Common Open Research Emulator)
http://www.nrl.navy.mil/itd/ncs/products/core
- Installation of the virtual machine of vcore 4.6 (available for VMware or VirtualBox)
http://downloads.pf.itd.nrl.navy.mil/core/vmware-image/

Objective: The objective is to implement and test a scenario of global routing involving multiple
Autonomous Systems (ASs) interconnected through the routing protocol BGP. Internally the ASs
use distinct routing protocols. The scenario to be emulated in the CORE platform is illustrated in
Figure 1.
Figure 1 - Scheme of the interconnection between various ASs and the used internal/external
routing protocols.
AS 65500
10.5.0.0/16
AS 65300
10.3.0.0/16
AS 65400
10.4.0.0/16
e-BGP
e-BGP
e-BGP e-BGP
AS 65000
10.0.0.0/16
OSPF
(area)
OSPF
(area)
OSPF
(area)
e-BGP
e-BGP
RIP
AS 65200
10.2.0.0/16
OSPF
(area)
RIP
AS 65100
10.1.0.0/16

Detailed Description:
1. The Autonomous System 65200 is a stub autonomous system. As such, it maintains
BGP peering relationships outside with a single AS neighbour that guarantees external
access: the AS 65400.
• The autonomous system 65200 uses internally the IPv4 address range 10.2.0.0/16.
• Internally, the autonomous system 65200 uses the RIP protocol, using default routes
to reach other autonomous systems.
• AS 65200 (network 10.2.0.0/16) has connectivity to all other ASs, with the
exception of AS 65100 for which the administrators of AS 65200 decided not to have
connectivity.
2. The Autonomous System 65100 is a stub autonomous system. As such, it maintains
BGP peering relationships outside with a single neighbour autonomous system that
guarantees external access: the AS 65300.
• Internally, the Autonomous System 65100 uses the OSPF routing protocol.
Additionally, there are also some older networks that operate according to the RIP
protocol. For connectivity between the networks/devices RIP/OSPF resorts to
processes of redistributing routes between them. Internally, default routes are used
to reach other autonomous systems.
• AS 65100 (network 10.1.0.0/16) has connectivity with all other ASs, with the
exception of AS 65200 for which the administrators of AS 65100 decided not to
have connectivity.
3. The Autonomous System AS 65000 is a multihomed autonomous system. As such, it
maintains BGP peering relationships outside with two neighbouring autonomous
systems which ensure that external access: AS 65300 and AS 65400.
• Internally, the Autonomous System 65000 uses the OSPF routing protocol,
structured in several areas (two areas beyond the area 0, and with at least three routers
in each area). Internally, default routes are used to reach other autonomous systems.
• It is guaranteed global connectivity to all networks of AS 65000 (10.0.0.0/16).
• The autonomous system 65000 AS is a multihomed system but not a transit
autonomous system. So, even if the connections between the neighbouring
autonomous systems AS 65300 and AS 65400 fails, they should not be able to route
traffic through autonomous system AS 65000.
4. The AS 65300, AS 65400 and AS 65500 are essentially transit autonomous systems.
As such, in the presented example, it is not strictly necessary to configure an internal
routing protocol into each one. However, it should be ensured that there is in each of
these autonomous systems at least one end system in the networks 10.3.0.0/16,
10.4.0.0/16 and 10.5.0.0/16, to perform connectivity tests between these and the
remaining ASs.

• The AS 65300 is the ISP of ASs 65100 and AS 65000. As such it must accept routes
advertised by them and disseminate them. In turn, the AS 65400 is the ISP of ASs
65200 and 65000. Likewise, it should accept and disseminate the routes advertised by
them.
Report:
Prepare a report describing the work performed and explaining the major decisions. As noted
before, the definition of the structure and content of the report is the responsibility of the working
groups. However, amongst others deemed relevant, do not forget to include in the report the
following topics:
• An explanation of the most relevant configuration commands of the internal protocols (OSPF
and RIP) made in different autonomous systems.
• An explanation of the performed BGP configurations, as well as how the external routing
policies (BGP) mentioned before were implemented. An analysis of the AS-PATH attributes
associated with the BGP routes exchanged between the peers.
• Commented examples of the routing tables of border AS routers. Moreover, relevant
commented examples of internal AS routers routing tables should also be mentioned.
• Connectivity tests demonstrating the compliance with the requirements presented.

UNIVERSITY OF MINHO
TECHNOLOGIES AND NETWORK PROTOCOLS
2015/2016
Routing
Part II - External/Internal Routing redistribution, conditioning
and filtering
Group 5
João Dias – PG30466
Khunbish Nyamsuren – E6769
Simão Dias – a61006

2
Table of Contents
Abstract.............................................................................................................4
Introduction ......................................................................................................5
Autonomous System 65200 Initialization....................................................6
Initial constraints for the initialization of AS 652000 ........................................ 6
Constraint a.............................................................................................................. 7
Constraint b.............................................................................................................. 7
Autonomous System 65100 Initialization....................................................8
Initial constraints for the initialization of AS 65100 .......................................... 8
Constraint a.............................................................................................................. 9
Constraint b.............................................................................................................. 9
Autonomous System 65000 Initialization................................................. 10
Initial constraints for the initialization of AS 65000 ........................................10
Constraint a............................................................................................................10
Constraint b............................................................................................................11
Autonomous System 65300, 65400 and 65500 Initialization............... 13
Constraint a. and b................................................................................................13
Globally connecting all Autonomous Systems.......................................... 14
Final constraints of the AS 65200.............................................................. 15
Final Constraint a. .................................................................................................15
Final Constraint b. .................................................................................................15
Final Constraint b. .................................................................................................19
Final Constraint b. and c.......................................................................................21
Final Topology............................................................................................... 23

Conclusion ..................................................................................................... 24
Table of Figures
Figure 1. AS 65200 Topology ................................................................................................. 6
Figure 2. AS 65100 Topology ................................................................................................. 8
Figure 3. AS 65000 Topology ...............................................................................................10
Figure 4. As 65300 Topology................................................................................................13
Figure 7. Pings from different hosts from AS65200 to a host of AS65100....................16
Figure 8. Pings from RIP PC1 to the different transit ASs................................................16
Figure 9. Pings from RIP PC2 to the different transit Ass ................................................17
Figure 10. Pings from RIP PC1 to the different areas of AS 65000................................17
Figure 11. Pings from RIP PC2 to the different areas of AS 65000................................17
Figure 12. Pings from hosts of AS 65200 to AS65100 OSPF side..................................18
Figure 13. Pings from AS 65200 different hosts to AS 65100 hosts on RIP side.........19
Figure 14. Ping to a OSPF host on AS65100......................................................................20
Figure 15. Ping to a RIP host on AS65100 .........................................................................20
Figure 16. Ping to RIP host on AS 65200 ...........................................................................20
Figure 17. Ping to a host on 65300 .....................................................................................21
Table Index
Table 1. Intra Network List for AS 65200 ............................................................................. 7
Table 2. AS 65200 protocols and default Routes ................................................................ 7
Table 3. Intra Network List for AS 65100 ............................................................................. 9
Table 4. AS 65100 protocols and default Routes on OSPF side and bridge router ........ 9
Table 5. AS 65100 protocols and default Routes on RIP side ........................................... 9
Table 6. Intra Network List for AS 65000 ...........................................................................10
Table 7. AS 65000 protocols, default Routes and areas...................................................11
Table 8. Routing protocols after BGP implementation .....................................................14

Abstract
In dynamic routing environments, IP routing information is propagated using routing
protocols. BGP is on of these protocols found in internet. Combining the knowledge we
obtained from the first project, with BGP protocol, the assistance of network emulation
software and a set of predefined questions, we will go more in depth on the
programming/configuration of network equipment in intra and inter nets that operate
under RIP, OSPF and/or BGP.
With BGP, we will put in practice a series of commands that allows us to restrict/filter
traffic from undesired Autonomous systems and the routing information from that one
AS propagates.
After this project we expect to be able to have a better understanding of this protocols
and the process that is required to accomplish a fully operating network.

Introduction
In this project we will further develop our knowledge with OSPF and RIP protocols, by
implementing redistribution routes between them.
The main focus, however, will be with the BGP protocol.
BGP protocol is a routing protocol for inter domains, it is used in the main internet
routers and for communication between different autonomous Systems(ASs).
BGP protocol came to solve EGP main problem, routing loops in arbitrary topologies
and allows routing based in a set of non-technical rules, defined by the different ASs.
The main function of a BGP system is to exchange information that allows network
access, including information about the routes of the ASs with other BGP systems.
When a router first connects to the network, BGP routes fully exchange their routing
tables. In a similar way, when a routing table changes, the routers send the changed
part of the routing table. Therefore, BGP routers are not regularly sending information,
and route actualizations are only felt on the optimal route to a network.
Also, BGP allows us to restrict/filter the information that is exchanged between BGP
systems, which allows to better control a vast network and its behaviour.
The document is split in two main parts, first we set, individually, the initial configuration
for the different required ASs as well as the imposed constraints.
In the second part, we globally connect all the ASs through the BGP protocol and, just as
before, configure the different ASs with the remaining constraints.

Autonomous System 65200 Initialization
Initial constraints for the initialization of AS 652000
a. Internally, uses the IPv4 address range 10.2.0.0/16
b. Internally, uses the RIP protocol, using default routes to reach other
autonomous systems.
We started by defining 3 routers and two hosts. The routers are all interconnected using
specific networks chosen by sub netting principles.
This autonomous System as the following representation:
Figure 1. AS 65200 Topology

Constraint a.
Table 1. Intra Network List for AS 65200
Intra Network List
1 10.2.0.0/24
2 10.2.1.0/24
3 10.2.2.0/24
4 10.2.3.0/24
5 10.2.4.0/24
Constraint b.
To check which protocols a router is using we used the command show running-config
on each of the routers and to see what default routes we take a look at the routing
tables with show ip route.
Table 2. AS 65200 protocols and default Routes
Router Protocol Default route
RIP1 router rip
…
!
RIP2 router rip
…
!
R>* 0.0.0.0/0 [120/2] via 10.2.0.1, eth0
(RIP1)
RIP3 router rip
…
!
R>* 0.0.0.0/0 [120/2] via 10.2.1.1, eth0
(RIP1)

b. Internally, uses the OSPF routing protocol.
c. Additionally, there are also some older networks that operate according
to the RIP protocol. For connectivity between the networks/devices
RIP/OSPF resorts to processes of redistributing routes between them,
using default routes to reach other autonomous systems.
This autonomous System is divided in 2 sides, one uses OSPF protocol while the other
uses RIP protocol. The RIP protocol side is not different from the AS 65200 in terms of
topology and the OSPF side has 1 router with one host. The connection between the RIP
and OSPF side is done by one router that includes both protocols and applies
redistribution.
This autonomous System as the following representation:

Constraint a.
Intra Network List
1 10.1.0.0/24
2 10.1.1.0/24
3 10.1.3.0/24
4 10.1.4.0/24
5 10.1.5.0/24
6 10.1.6.0/24
7 10.1.7.0/24
8 10.1.8.0/24
Constraint b.
Protocol was checked with the show running-config command.
Default Route was checked with the show ip route command.
Table 4. AS 65100 protocols and default Routes on OSPF side and bridge router
R-OSPF1 router ospf
redistribute rip metric 5
…
!
router rip
redistribute ospf metric 7
…
!
R-OSPF2 router ospf O>* 0.0.0.0/0 [110/1] via 10.1.1.1, eth0
(R-OSPF1)
Table 5. AS 65100 protocols and default Routes on RIP side
O-RIP1 router rip O>* 0.0.0.0/0 [120/2] via 10.1.0.2, eth2
(R-OSPF1)
O-RIP2 router rip R>* 0.0.0.0/0 [120/3] via 10.1.4.1, eth0
(O-RIP1)
O-RIP3 router rip R>* 0.0.0.0/0 [120/3] via 10.1.5.1, eth0
(O-RIP1)

b. Internally, uses OSPF routing protocol, structured in several areas (two
areas beyond the area 0, and with at least three routers in each area),
using default routes to reach other autonomous systems.
This AS requires to run only with OSPF protocol with 3 different areas with at least 3
routers each. We chose to have 3 routers on the backbone area (area 0) and 4 on the
other 2 areas. The router A1-R1 and A2-R2 are routers that do the connection between
area 1 and area 2, respectively, with area 0.
For this autonomous system we chose the following topology:
Constraint a.
Intra Network List Area
1 10.0.100.0 0.0.0.0
2 10.0.200.0 0.0.0.0

3 10.0.101.0 0.0.0.1
4 10.0.102.0 0.0.0.1
5 10.0.103.0 0.0.0.1
6 10.0.104.0 0.0.0.1
7 10.0.105.0 0.0.0.1
8 10.0.106.0 0.0.0.1
9 10.0.107.0 0.0.0.1
10 10.0.108.0 0.0.0.1
11 10.0.201.0 0.0.0.2
12 10.0.202.0 0.0.0.2
13 10.0.203.0 0.0.0.2
14 10.0.204.0 0.0.0.2
15 10.0.205.0 0.0.0.2
16 10.0.206.0 0.0.0.2
17 10.0.207.0 0.0.0.2
18 10.0.208.0 0.0.0.2
Constraint b.
Default Route was checked with the show ip route command.
The are was obtained with the show ip ospf command
Table 7. AS 65000 protocols, default Routes and areas
Router Protocol Default Route Area
A0-R1 router ospf 0.0.0.0
A1-R1 router ospf O>* 0.0.0.0/0 [110/1] via 10.0.100.1, eth2
(A0-R1)
0.0.0.0 and
0.0.0.1
(A1-R1)
0.0.0.1
(A1-R1)
0.0.0.1
(A1-R1)
0.0.0.1
(A0-R1)
0.0.0.0 and
0.0.0.2

(A2-R1)
0.0.0.2
(A2-R1)
0.0.0.2
(A2-R1)
0.0.0.2

Autonomous System 65300, 65400 and 65500
Initialization
a. Essentially transit autonomous systems.
b. They should have an end system for connectivity tests.
Constraint a. and b.
Figure 4. As 65300 Topology

Globally connecting all Autonomous Systems
To connect all the autonomous systems, the required protocol used is BGP.
Only one router from each AS has the implementation of this protocol (routers used in
default routes), to do this we changed the configuration to guarantee that beside the
already applied protocols, they also implement BGP.
Table 8 only shows the routers that were affected by the insertion of the BGP protocol.
Table 8. Routing protocols after BGP implementation
Autonomous System Router that implements BGP Implemented Protocols
65000 A0-R1 BGP and OSPF
65100 R-OSPF1 RIP, OSPF and BGP
65200 RIP1 RIP and BGP
65300 AS65300 BGP
65400 AS65400 BGP
65500 AS65500 BGP

Final constraints of the AS 65200
a. Has connectivity with all other ASs, with the exception of 65100.
b. Maintains BGP peering relationship outside with a single AS neighbour
that guarantees external access: the AS 65400.
Final Constraint a.
To cut the connectivity between two autonomous systems we make use of access-lists.
First we enter the router configuration mode responsible for the BGP protocol (RIP1)
with the command config terminal.
And after we create two access-lists with the command access-list 1 deny 10.1.0.0
0.0.255.255 and access-list 1 permit any
• Access-list: initialization of the command.
• 1: means that it is an IP standard access list
• deny 10.1.0.0 0.0.255.255: filters the traffic that comes from the
network 10.1.0.0 with the 0.0.255.255 as wildcard bits (10.1.0.0/16).
• Permit any: permits any traffic.
Note that the permit any access-list does not override the previously created access-lists.
If we now see the running-configuration of RIP1 we can see
access-list 1 deny 10.1.0.0 0.0.255.255
access-list 1 permit any
Final Constraint b.
To achieve this, we enter the router configuration mode responsible for the the BGP
protocol(R-OSPF1) with the command config terminal followed by router bgp 65200.
In here, we can set the neighbors with the commands neighbor 1.1.1.1 remote-as
65400.

To see if the access-list is working we perform connectivity tests:
Figure 7. Pings from different hosts from AS65200 to a host of AS65100
Figure 8. Pings from RIP PC1 to the different transit ASs

Figure 9. Pings from RIP PC2 to the different transit Ass
Figure 10. Pings from RIP PC1 to the different areas of AS 65000
Figure 11. Pings from RIP PC2 to the different areas of AS 65000

a. Has connectivity with all other ASs, with the exception of 65200.
b. Maintains BGP peering relationship outside with a single AS neighbour
that guarantees external access: the AS 65300.
Final Constraint a.
To cut the connectivity between two autonomous systems we follow the same procedure
as last AS:
First we enter the router configuration mode responsible for the BGP protocol (R-
OSPF1) with the command config terminal.
And after we create two access-lists with the command access-list 1 deny 10.2.0.0
0.0.255.255 and access-list 1 permit any
• Access-list: initialization of the command.
• 1: means that it is an IP standard access list
• deny 10.2.0.0 0.0.255.255: filters the traffic that comes from the
network 10.2.0.0 with the 0.0.255.255 as wildcard bits (10.2.0.0/16).
• Permit any: permits any traffic.
Note that the permit any access-list does not override the previously created access-lists.
If we now see the running-configuration of RIP1 we can see
access-list 1 deny 10.2.0.0 0.0.255.255
access-list 1 permit any
To see if the access-list is working we perform connectivity tests:
Figure 12. Pings from hosts of AS 65200 to AS65100 OSPF side

Figure 13. Pings from AS 65200 different hosts to AS 65100 hosts on RIP side
Final Constraint b.
protocol(R-OSPF1) with the command config terminal followed by router bgp 65100.
65300.

a. It is guaranteed global connectivity to all networks.
b. Is multihomed system but not a transit autonomous system.
c. Maintains BGP peering relationship outside with two neighbouring ASs
that guarantees external access: the AS 65300 and the AS 65400.
Final Constraint a.
As default, this autonomous system is fully connected to every other autonomous
system. To prove it, we preform connectivity tests to a host on every other ASs.
Figure 14. Ping to a OSPF host on AS65100
Figure 15. Ping to a RIP host on AS65100
Figure 16. Ping to RIP host on AS 65200

Figure 17. Ping to a host on 65300
We can conclude that AS 65000 is fully connected to all other ASs with no restrictions.
Final Constraint b. and c.
First we make sure that AS 65300 and 65400 are neighbors to this AS.
protocol(A0-R1) with the command config terminal followed by router bgp 65000.
65300 and neighbor 5.5.5.1 remote-as 65400.
To guarantee this AS in never used as transit we make use of as-paths.
First we enter the router configuration mode responsible for the BGP protocol (A0-R1)
with the command config terminal.
Here, we use the command ip as-path access-list 1 permit ^$. ^$ stands for locally
originated routes.

After, we create the route map with the commands
route-map ISP permit 10
match as-path 1
(which is the one we previously created).
Finally, we apply the route-map to outbound routes with the commands
Router bgp 65000
Neighbor 6.6.6.1 route-map ISP out
Neighbor 5.5.5.1 router-map ISP out
To prove that AS 65000 doesn’t act as transit first we pinged from a host of 65200 to
the host of AS 65300.
We can see that we still have connectivity because it took the route AS65200-
>AS65400->AS65300->host
Now, if we shutdown interface eth2 from AS65400 and redo the ping test:
We can see that the destination is not reachable, which means AS6500 is not used as
transit.
However, if we ping to a local host of AS6500:
We are able to have connectivity.

Conclusion
With this work we had the opportunity to further develop our knowledge with the intra
network protocols OSPF and RIP. It also allowed us to better understand their
functioning regarding redistribution and intra communication.
The experiments done with the BGP protocol, how to restrain the routes that BGP
system exchange between each other as well as traffic filtering from unwanted
connections permitted us to have a better vision on how inter networks function, behave,
how they can interact between different ASs and how they can be configured to perform
the way a network manager desires. It was also important to notice how as-paths can be
used to prevent routing loops.

BGP and multi OSPF and RIP

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