Yu Cheng (Jade) ICS 351 Lab Report 4 part 3 October 26, 2008 [Exercise 5A-5B] We connected the ethernet interfaces of the PCs and the routers. We used the following commands to configure the IP addresses and the interfaces on the PCs: on PC1: `ifconfig eth0 10.0.1.1/24` on PC1: `ifconfig eth1 10.0.2.1/24` on PC2: `ifconfig eth0 10.0.1.2/24` on PC2: `ifconfig eth1 10.0.5.2/24` on PC3: `ifconfig eth0 10.0.3.4/24` on PC3: `ifconfig eth1 10.0.4.4/24` on PC4: `ifconfig eth0 10.0.6.7/24` on PC4: `ifconfig eth1 10.0.7.7/24` We used the following commands to turn on the OSPF protocol and configure the IP addresses and interfaces on the routers: on PC1: `minicom` username: cisco password: cisco yourname# config t yourname(config)# no ip routing yourname(config)# ip routing yourname(config)# no router rip yourname(config)# router ospf 1 yourname(config-router)# network 10.0.0.0 255.255.255 area 1 yourname(config-router)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.3.3 255.255.255.0 yourname(config-if)# interface fa0/1 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.2.3 255.255.255.0 yourname(config-if)# end yourname# clear ip route * yourname(config)# router ospf 1 yourname(config-router)# network 10.0.0.0 255.255.255 area 1 yourname(config-router)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.4.5 255.255.255.0 yourname(config-if)# interface fa0/1 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.2.5 255.255.255.0 yourname(config-if)# end yourname# clear ip route * yourname(config)# router ospf 1 yourname(config-router)# network 10.0.0.0 255.255.255 area 1 yourname(config-router)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.5.6 255.255.255.0 yourname(config-if)# interface fa0/1 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.6.6 255.255.255.0 yourname(config-if)# end yourname# clear ip route * yourname(config)# router ospf 1 yourname(config-router)# network 10.0.0.0 255.255.255 area 1 yourname(config-router)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.5.8 255.255.255.0 yourname(config-if)# interface fa0/1 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.7.8 255.255.255.0 yourname(config-if)# end yourname# clear ip route * We configured the PCs to run OSPF using the Zebra package. We first enabled IP forwarding on the PCs and added the Zebra directory to the path. The commands we used were as follows: on PC#: `echo "1" > /proc/sys/net/ipv4/ip_forward` on PC#: `export PATH=/etc/rc.d/init.d/:$PATH` on PC#: `zebra start` on PC#: `ripd stop` on PC#: `ripd status` on PC#: `zebra restart` on PC#: `ospfd start` on PC#: `telnet localhost 2604` Since this was the begining of the lab and we didn't run ripd on the machines before this exercise, the commands `ripd stop` was not needed. We further configured the PCs to run ospfd. We used commands: ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# network 10.0.0.0/8 area 1 ospf(config-router)# router-id 10.0.1.1 ospf(config-router)# no passive-interface eth0 ospf(config-router)# no passive-interface eth1 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# network 10.0.0.0/8 area 1 ospf(config-router)# router-id 10.0.1.2 ospf(config-router)# no passive-interface eth0 ospf(config-router)# no passive-interface eth1 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# network 10.0.0.0/8 area 1 ospf(config-router)# router-id 10.0.3.4 ospf(config-router)# no passive-interface eth0 ospf(config-router)# no passive-interface eth1 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# network 10.0.0.0/8 area 1 ospf(config-router)# router-id 10.0.6.7 ospf(config-router)# no passive-interface eth0 ospf(config-router)# no passive-interface eth1 ospf(config-if)# end ospf# exit We used traceroute and ping commands to verify the configuration. The commands did not go through at first. We added 'no shutdown' to configure the routers' interfaces and issued the commands again. This time, they were successful. We also used command `netstat -rn` on the PCs and command `show ip route` on the routers to display the routing tables. The hosts and routers all had routing information of the other networks in the system. [Exercise 5C] We started the wireshark on PC1 and set a display filter to display only OSPF packets. We issued a traceroute from PC3 to PC4 using `traceroute 10.0.7.7`. We observed that the packets went from PC3 to Router 2 to PC1 to PC2 to Router4 and reached PC4. 10.0.4.4 10.0.4.5 10.0.2.1 10.0.1.2 10.0.5.8 10.0.7.7 We started a ping command from PC3 to PC4 `ping 10.0.7.7` with no time limitation. We then disconnected the interface 0 on Router4. This disconnection removed Router4 from the picture. Question 5-a We observed that it was very fast for the system to reestablish the connections. We terminated the ping command by typing "Ctrl-C". By looking at the ping statistics, we observed a 2% packets loss. We lost 6 out of 231 packets. Therefore the connection was down for 6 secondes. -------------------------- 10.0.7.7 ping statistics --------------------------- 231 packets transmitted, 225 received, 2% packet loss, time 230577ms rtt min/avg/max/mdev = 0.715/0.917/1.149/0.064 ms ------------------------------------------------------------------------------- Question 5-b We observed 3 OSPF LS Update packets and 2 OSPF LS Acknowledge packets. The rest of the OSPF packets were Hello packets. Question 5-c The OSPF LS Update packets were used for flooding link state information. Question 5-d When there are no network changes, OSPF will use very little bandwidth (only sending hello packets). As soon as there is an outage, however, OSPF will flood the network as the change is sent to every router, and then every router notifies every other router in its area about the change. In the system, there is very little network traffic when there are no route updates, and the network is flooded when there are updates and information gets propagated throughout the network as quickly as possible. Question 5-e OSPF runs directly over the Internet Protocol's network layer. OSPF packets are therefore encapsulated solely by IP and local data-link headers. OSPF does not define a way to fragment its protocol packets and depends on IP fragmentation when transmitting packets larger than the network MTU. The OSPF packet types that are likely to be large, such as LS Update and LS Acknowledgment packets, can usually be split into several separate protocol packets without loss of functionality. In the OSPF packets that we saved, we saw "Type: IP (0x0800)". Question 5-f The destination address of OSPF packets is 224.0.0.5. The range from 224.0.0.0 to 224.0.0.255 is designated for multicasting on the local LAN only. Well-known examples are RIPv2 which uses 224.0.0.9 and OSPF which uses the 224.0.0.5. We saved the ping staticstics as ex5c-7.txt. We also saved the reestablished traceroute output into the same file. After the re-connection, the packets from PC3 to PC4 went through Router2, PC1, PC2, and Router3. 10.0.4.4 10.0.4.5 10.0.2.1 10.0.1.2 10.0.5.6 10.0.7.7 We saved the link state database on all PCs and routers as ex5c-9routers.txt, ex5c-9PC1.txt, ex5c-9PC2.txt, ex5c-9PC3.txt, and ex5c-9PC4.txt. The entities were the same. We verified that all routers and PCs indeed had the same link-stated database. --------------------------Router Link States (Area 1)-------------------------- Link ID ADV Router 10.0.1.1 10.0.1.1 10.0.1.2 10.0.1.2 10.0.2.3 10.0.2.3 10.0.2.5 10.0.2.5 10.0.3.4 10.0.3.4 10.0.5.6 10.0.5.6 10.0.5.8 10.0.5.8 10.0.6.7 10.0.6.7 ---------------------------Net Link States (Area 1)---------------------------- Link ID ADV Router 10.0.1.2 10.0.1.2 10.0.2.1 10.0.1.1 10.0.3.4 10.0.3.4 10.0.4.4 10.0.3.4 10.0.5.2 10.0.1.2 10.0.6.6 10.0.5.6 10.0.7.8 10.0.5.8 We also stopped the wireshark and saved one packet for each of the three types of OSPF packets we observed. They are ex5c-10-1.txt, OSPF LS Update, ex5c-10-2.txt, OSPF LS Acknowledge, ex5c-10-3.txt, and OSPF Hello Packet. [Exercise 6] We reconfigured the PCs and routers to assgin different area numbers to these network entities. We first restarted ospfd using `zebra restart` and `ospfd restart`. We then used the following commands to configure the area numbers: ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# router-id 10.0.3.4 ospf(config-router)# network 10.0.3.0/24 area 1 ospf(config-router)# network 10.0.4.0/24 area 1 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# router-id 10.0.6.7 ospf(config-router)# network 10.0.6.0/24 area 2 ospf(config-router)# network 10.0.7.0/24 area 2 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# router-id 10.0.1.1 ospf(config-router)# network 10.0.2.0/24 area 1 ospf(config-router)# network 10.0.1.0/24 area 0 ospf(config-if)# end ospf# exit ospf> enable ospf# config t ospf(config)# router ospf ospf(config-router)# router-id 10.0.1.2 ospf(config-router)# network 10.0.5.0/24 area 2 ospf(config-router)# network 10.0.1.0/24 area 0 ospf(config-if)# end ospf# exit yourname# config t yourname(config)# no router ospf 1 yourname(config)# router ospf 1 yourname(config-router)# network 10.0.3.0 0.0.0.255 area 1 yourname(config-router)# network 10.0.2.0 0.0.0.255 area 1 yourname(config-router)# end yourname # clear ip ospf 1 process yourname# config t yourname(config)# no router ospf 1 yourname(config)# router ospf 1 yourname(config-router)# network 10.0.2.0 0.0.0.255 area 1 yourname(config-router)# network 10.0.4.0 0.0.0.255 area 1 yourname(config-router)# end yourname # clear ip ospf 1 process yourname# config t yourname(config)# no router ospf 1 yourname(config)# router ospf 1 yourname(config-router)# network 10.0.5.0 0.0.0.255 area 2 yourname(config-router)# network 10.0.6.0 0.0.0.255 area 2 yourname(config-router)# end yourname # clear ip ospf 1 process yourname# config t yourname(config)# no router ospf 1 yourname(config)# router ospf 1 yourname(config-router)# network 10.0.5.0 0.0.0.255 area 2 yourname(config-router)# network 10.0.7.0 0.0.0.255 area 2 yourname(config-router)# end yourname # clear ip ospf 1 process We displayed the link-stated databases using command `show ip ospf datasase` on the routers and command `show ip ospf database` on the PCs. We saved the link state databases of the PCs and router as ex6-4PC1.txt, ex6-4PC2.txt, ex6-4PC3.txt, ex6-4PC4.txt, and ex6-4routers.txt. Question 4-a In the PCs' databases, we observed data for two areas in PC1 and PC2. PC1 had area 10.0.0.0 and area 10.0.0.1. PC2 had area 10.0.0.0 and area 10.0.0.2. PC3 had area 10.0.0.1. PC4 had area 10.0.0.2. In exercise 5, there was data for only one area, 10.0.0.1, in all the PCs' link-state databases. In the routers' databases, we observed that Router1 and Router2 belonged to area 1. Router3 and Router4 belonged to area 2. In excercise 5, the routers belonged to area 1. Question 4-b Routers in area 1 know all about the networks on the other side, and this information was advertised by PC1. -----------------------Summary Net Link States (Area 1)------------------------ Link ID ADV Router 10.0.1.0 10.0.1.1 10.0.5.0 10.0.1.1 10.0.6.0 10.0.1.1 10.0.7.0 10.0.1.1 ------------------------------------------------------------------------------- A router has a separate link state database for every area to which it belongs. All routers belonging to the same area have identical topological databases for the area. Therefore, the summary above is for both Router1 and Router2. Question 4-c Routers in area 0, the backbone area, know all about the networks in area 1 and area 2. This information was advertised by either PC1 or PC2. ----------------------Summary Link States (Area 0.0.0.0)----------------------- Link ID ADV Router 10.0.2.0 10.0.1.1 10.0.3.0 10.0.1.1 10.0.4.0 10.0.1.1 10.0.5.0 10.0.1.2 10.0.6.0 10.0.1.2 10.0.7.0 10.0.1.2 ------------------------------------------------------------------------------- The summary above is for both PC1 and PC2 because they belong to the same area. Question 4-d As described in the two tables above, PC1 advertised the topology of area 2 to the PCs and the routers in area 1. PC1 obtained this information from PC2. PC2 advertised the topology of area 1 to PCs and routers in area2. PC2 obtained this information from PC1. We then displayed the area routers known to Router1 and area 1 using command `show ip ospf border-routers`. We saved the output to the same file, ex6-4routers.txt. This command displays the internal OSPF routing table entries to an Area Border Route (ABR) and Autonomous System Boundary Router (ASBR). --------------------------show ip ospf border-routers-------------------------- OSPF Process 1 internal Routing Table Codes: i - Intra-area route, I - Inter-area route i 10.0.1.1 [1] via 10.0.2.1, FastEthernet0/1, ABR, Area 1, SPF 10 ------------------------------------------------------------------------------- As shown in the output, the border router for Router1 is PC1, 10.0.1.1. Information from outside of area 1 would go through 10.0.1.1 and 10.0.2.1 to the interface 0/1 on Router1. This is how Router1 learns about other networks that are outside of area 1. We obversved two types of OSPF packets that we did not observe previously. They were OSPF DB Descr packets and OSPF LS Request packets. We saved one OSPF DB Descr packet as ex6-6-1.txt and one OSPF LS Request packet as ex6-6-2.txt. [Exercise 7] We disconnected the cables and connected them with a new setup. We started the wireshark on PC4 at the beginning of the exercise. We disabled OSPF processes that were running using command `no router ospf 1`. We stopped the zebra process on all PCs using command `zebra stop`. Since the lab PCs run BGP but the routers don't, we configured the PCs as routers and the routers as PCs. We first manually changed the AS numbers of the PCs. We used the following command to display the content of the configuration setup. We change the As number to 100 for PC1, 200 for PC2, and 300 for PC3. We saved and closed the files. on PC#: `gedit /etc/quagga/bgpd.conf` We realized later that we could also do it using command `router bgp #`. We restarted zebra and bgpd. We used the following command to configure the PCs. on PC1: `telnet localhost 2605` username: cisco password: cisco bgp> enable bgpd# config t bgpd(config)# router bgp 100 bgpd(config-router)# neighbor 10.0.4.2 remote-as 200 bgpd(config-router)# neighbor 10.0.4.3 remote-as 300 bgpd(config-if)# end bgpd# exit on PC2: `telnet localhost 2605` username: cisco password: cisco bgp> enable bgpd# config t bgpd(config)# router bgp 200 bgpd(config-router)# neighbor 10.0.4.1 remote-as 100 bgpd(config-router)# neighbor 10.0.4.3 remote-as 300 bgpd(config-if)# end bgpd# exit on PC3: `telnet localhost 2605` username: cisco password: cisco bgp> enable bgpd# config t bgpd(config)# router bgp 200 bgpd(config-router)# neighbor 10.0.4.1 remote-as 100 bgpd(config-router)# neighbor 10.0.4.2 remote-as 200 bgpd(config-if)# end bgpd# exit on PC4: `zebra stop` on PC4: `bgpd stop` We used the following commands to configure the routers: yourname# config t yourname(config)# ip route 10.0.0.0 255.0.0.0 10.0.1.1 yourname(config)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.1.10 255.255.255.0 yourname# config t yourname(config)# ip route 10.0.0.0 255.0.0.0 10.0.2.2 yourname(config)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.2.10 255.255.255.0 yourname# config t yourname(config)# ip route 10.0.0.0 255.0.0.0 10.0.3.3 yourname(config)# interface fa0/0 yourname(config-if)# no shutdown yourname(config-if)# ip address 10.0.3.10 255.255.255.0 We issued ping commands and traceroutes to verify the configuration. We observed successful connections between PCs and routers. We saved the output of the following commands as ex7a-7router1.txt, ex7a-7router2.txt, and ex7a-7router3.txt. on PC# netstat -rn bgpd# show ip bgp bgpd# show ip bgp paths Question 7-a We observed only one type of BGP packets. They were KEEPALIVE messages. BGP sends 19 bytes long KEEPALIVE messages at an interval specified by the KEEPALIVE Interval timer in the BGP router configuration (the default is 60 seconds). If a BGP peer misses three keepalives (180 seconds) all routes from that peer are suppressed according to the holdtime timer setting. The holdtime timer determines how long a peer should wait to hear a KEEPALIVE or UPDATE message before assuming the neighbor is down, shutting down the BGP session, and withdrawing all routes from its announcements. Question 7-b The main reason is reliability. BGP is a unicast protocol. It needs to be secure and reliable. TCP transmission uses three-way handshaking. Two Ack messages are required for a successful communication. Also, BGP defines neighbors manually, and there is no periodic update in BGP. The update and database is big. Since we don't repeat the sending periodically, reliability is very important. Question 7-c The next-hop attribute for AS 100 on Router2 is 10.0.4.1. As we can see in the routing table below, the Gateway for network 10.0.1.0 is 10.0.4.1. ---------------------------[root@PC2 ~]# netstat -rn--------------------------- Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.4.0 0.0.0.0 255.255.255.240 U 0 0 0 eth1 10.0.1.0 10.0.4.1 255.255.255.0 UG 0 0 0 eth1 10.0.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.0.3.0 10.0.4.3 255.255.255.0 UG 0 0 0 eth1 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 ------------------------------------------------------------------------------- Question 7-d BGP peers are BGP neighbors. They are established by manual configuration between routers to create a TCP session on port 179. In this topology, the neighboring AS 100, AS 200, and AS 300 are BGP peers. We stopped the wireshark and saved the output as file ex7a-7wireshark.txt. An AS-PATH is a sequence of intermediate ASs between source and destination routers that form a directed route for packets to travel. Neighboring ASs use BGP to exchange update messages about how to reach different AS prefixes. After each router makes a new local decision on the best route to a destination, it will send that route, or path information, along with accompanying distance metrics and path attributes, to each of its peers. As this information travels through the network, each router along the path prepends its unique AS number to a list of ASs in the BGP message. This list is the route's AS-PATH. An AS-PATH in conjunction with an AS prefix provides a specific handle for a one-way transit route through the network. [Exercise 7b] We saved the output of command `show ip bgp neighbors` on Router2 as ex7b-1.txt. We started wireshark on PC4 with a display filter "bgp". We configured the routers (PCs in this exercise) to use a shorter keepalive timer and a shorter holdtime timer. We then disconnected the cable of interface 1 on Router1 (PC1). on PC#: `telnet localhost 2605` username: cisco password: cisco bgp> enable bgpd# config t bgpd(config)# router bgp # bgpd(config-router)# timers bgp 10 30 bgpd(config-if)# end bgpd# exit Question 4-a The KEEPALIVE messages were constantly sent to the peers. When KEEPALIVE messages went down, after the certain period of time the peers would assume this connection had gone down. Question 4-b The BGP UPDATE Message indicated that there was a link problem. We saved the detail of one BGP UPDATE Message as ex7b-4.txt We displayed the neighbor information using `show ip bgp neighbors` on Router3 (PC3). We saved them as ex7b-5ROUTER3.txt. We also saved the routing table of Router2 and Router3 (PC2 and PC3) as ex7b-6ROUTER2.txt and ex7b-6ROUTER3.txt. ---------------------------[root@PC2 ~]# netstat -rn--------------------------- Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.4.0 0.0.0.0 255.255.255.240 U 0 0 0 eth1 10.0.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.0.3.0 10.0.4.3 255.255.255.0 UG 0 0 0 eth1 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 ---------------------------[root@PC3 ~]# netstat -rn--------------------------- Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.4.0 0.0.0.0 255.255.255.240 U 0 0 0 eth1 10.0.2.0 10.0.4.2 255.255.255.0 UG 0 0 0 eth1 10.0.3.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 From the routing tables above, we observed that the entry for network 10.0.1.0 was gone. We stopped the wireshark and saved the output as ex7b-7.txt