IP1 (2) IP Routing (version 2)
Hervé TREMEUR AT&T Labs AT&T Global Network
[email protected] IP1 Training
CISCO router introduction
Contents 1. Review y IP Addressing y Exercises 1 and 2
2. What is routing y How are processed the received framed packets y Route Table y Static and Dynamic Routes
3. Static Routing y Static Routing Internetwork y Static Routing configuration y Route Table example ( Cisco Router)
CISCO router introduction
Contents (cont. 1) 3. Static Routing (cont.) y y y y y y
Exercice 3 : internetwork and route table Route table lookup for packet flow Case Study 1 :Simple Static routes 3 steps : Simple Static route configuration Case Study 2 : Summary routes (1) Case Study 3 : Floating static routes (1)
4. Exercises 3. LAB on Static Routing y
Exercice 3 with configuration on Cisco Routers
CISCO router introduction
IP Address Classes 1
8
9
16
17
24
25
Class A:
0NNNNNNN
Host
Host
Host
Class B:
10NNNNNN
Network
Host
Host
Network
Network
Class C: Class D:
y y y y y
110NNNNN
1110MMMM
Multicast
Multicast
32
Host
Multicast
Class A : First bit is 0 , Network 1.0.0.0 to 126.0.0.0, 127 networks,16 777 216 Hosts Class B : First 2 bits 10 , Network 128.0.0.0 to 191.255.0.0, 16384 networks, 65 536 Hosts Class C : First 3 bits 110 , Network 192.0.0.0 to 223.255.255.0, 2097152 networks, 254 Hosts Class D : First 4 bits 1110 , Network 224.0.0.0 to 239.255.255.255 10.0.0.0, 172.16.0.0 to 172.31.0.0 and 192.168.0.0 are private and not used in public network.
CISCO router introduction
Determining Available Host Addresses Network
Host
172
16
0
0
10101100
00010000
00000000
00000000
00000000
00000001
00000000
00000010
11111111
11111111
65536
2**(N)-2 = 2**(16)-2 =65534
y Once the network portion is determined, we can determine the total number of Hosts by the formula 2 **(N) – 2
y Subtract 2 ( 1 address of all 0s for network , 1 address of all 1s for broadcast address)
CISCO router introduction
Decimal Equivalent of Bit Patterns 128
64
32
16
8
4
2
1
0
0
0
0
0
0
0
0
=
0
1
0
0
0
0
0
0
0
=
128
1
1
0
0
0
0
0
0
=
192
1
1
1
0
0
0
0
0
=
224
1
1
1
1
0
0
0
0
=
240
1
1
1
1
1
0
0
0
248
1
1
1
1
1
1
0
0
= =
1
1
1
1
1
1
1
0
254
1
1
1
1
1
1
1
1
= =
252
255
y Subnet bits come from the high-order bits of the host field y To determine a subnet mask for an address, add the decimal value of each position that has a 1 in it . For example : 224 = 128 + 64 + 32
CISCO router introduction
Class B Subnet Example IP Host Address : 172.16.2.121, Subnet Mask : 255.255.255.0
NETWORK
SUBNET
HOST
172.16.2.121
10101100
00010000
00000010
01111001
Host
255.255.255.0
11111111
11111111
11111111
00000000
Mask
172.16.2.0
10101100
00010000
00000010
00000000
172.16.2.255
10101100
00010000
00000010
11111111
Subnet Broadcast
172.16.2.1
10101100
00010000
00000010
00000001
First
172.16.2.254
10101100
00010000
00000010
11111110
Last
y This network has eight bits of subnetting that provide up to 254 subnets and 254 hosts addresses
CISCO router introduction
Class B Subnet Example (cont.) Number of bits
Subnet Mask
Number of Subnets
Number of Hosts / Subnet
17
255.255.128.0
2
32766
18
255.255.192.0
4
16382
19
255.255.224.0
8
8190
20
255.255.240.0
16
4094
21
255.255.248.0
32
2046
22
255.255.252.0
64
1022
23
255.255.254.0
128
510
24
255.255.255.0
256
254
25
255.255.255.128
512
126
26
255.255.255.192
1024
62
27
255.255.255.224
2048
30
28
255.255.255.240
4096
14
29
255.255.255.248
8192
6
30
255.255.255.252
16384
2
CISCO router introduction
Class C Subnet Planning Example 1 IP Host Address : 192.16.2.121, Subnet Mask : 255.255.255.248
NETWORK
Network
Subnet Host
11000000
00010000
00000010
01111 ! 001
Host
255.255.255.248 11111111
11111111
11111111
11111 ! 000
Mask
192.16.2.120
11000000
00010000
00000010
01111 ! 000
192.16.2.127
11000000
00010000
00000010
192.16.2.121
11000000
00010000
00000010
01111 ! 001
192.16.2.126
11000000
00010000
00000010
01111 ! 110
192.16.2.121
y
Subnet 01111 ! 111 Broadcast First Last
CISCO router introduction
Exercise 1 : Class C Subnet Planning Example 2 IP Host Address : 192.16.2.121, Subnet Mask : 255.255.255.252
NETWORK
Network
Subnet Host 011110 ! 01
10101100
00010000
00000010
255.255.255.252 11111111
11111111
11111111
11000000
00010000
00000010
11000000
00010000
00000010
11000000
00010000
00000010
11000000
00010000
00000010
192.16.2.121
Host Mask Subnet Broadcast First Last
y Determine the subnet, the broadcast address, the first and last host addresses
CISCO router introduction
Exercise 1 : Result IP Host Address : 192.16.2.121, Subnet Mask : 255.255.255.252
NETWORK
Network
Subnet Host
11000000
00010000
00000010
011110 ! 01
Host
255.255.255.252 11111111
11111111
11111111
111111 ! 00
Mask
192.16.2.120
11000000
00010000
00000010
011110 ! 00
192.16.2.123
11000000
00010000
00000010
192.16.2.121
11000000
00010000
00000010
011110 ! 01
192.16.2.122
11000000
00010000
00000010
011110 ! 10
192.16.2.121
y
Subnet 01111 0 ! 11 Broadcast First Last
CISCO router introduction
Exercice 2 : Class C Subnet Planning Example 3 All subnets used 10 Hosts / subnet Class C Address 192.168.5.0
y With this Class C Address 192.168.5.0, How many subnets containing at least 10 Hosts can be configured (We assumed that we have more than 4 routers and enough Ethernet interfaces )
CISCO router introduction
Exercice 2 : Class C Subnet Planning Example 3 (result) All subnets used 10 Hosts / subnet Class C Address 192.168.5.64
192.168.5.16 192.168.5.0
192.168.5.32 y With IP subnet zero configured on router y First subnet : 192.168.5.0 y Last subnet : 192.168.5.248 y 16 subnets possible
192.168.5.48
192.168.5.0
CISCO router introduction
Variable Length Subnet Masks (VLSM) Class B 156.26.0.0 /16 ---------- 156.26.1.0 / 24 156.26.2.0 / 24--------156.26.2.0 / 30 156.26.2.4 / 30 156.26.2.8 / 30 ……………… 156.26.2.252 / 30 -------------------------------------------------------------------------126 62 30 14 6 2 I N Hosts --------------------------------------------------------I----------------128 64 32 16 8 4 2 1 I ------------------------------------------------------- I-----------------25 26 27 28 29 30 32 I N Bits in mask --------------------------------------------------------I--- -------------128 192 224 240 248 252 I Mask
------------------------------------------- -i--------------
CISCO router introduction
Variable Length Subnet Masks (VLSM) (cont.)
192.168.50.0 ETHERNET
10 Hosts 100 Hosts Serial Link
2 Hosts Token-ring
ETHERNET 50 Hosts
ETHERNET 20 Hosts
y Use VLSM to allow the class C 192.168.50.0 to accommodate this internetwork and the hosts on each on the data link.
CISCO router introduction
Variable Length Subnet Masks (VLSM) (cont.) Data Link Token Ring
Subnet
Mask
192.168.50.128
255.255.255.128
N Bits 25
Hosts IP Addresses (Used)
Total
Needed
Hosts
Hosts
192.168.50.129
126
100
to
62
50
to
30
20
to
14
10
to
192.168.50.254 Ethernet
192.168.50.64
255.255.255.192
26
192.168.50.65 192.168.50.126
Ethernet
192.168.50.32
255.255.255.224
27
192.168.50.33 192.168.50.62
Ethernet
192.168.50.16
255.255.255.240
28
192.168.50.17 192.168.50.30
Free
192.168.50.1
to
192.168.50.15
Class C 192.168.50.0 / 24 ---------- 192.168.50.128 / 25 192.168.50.0 / 25 -------192.168.50.64 / 26 192.168.50.0 / 26 ------ 192.168.50.32 / 27
CISCO router introduction
What is Routing ?
W o rk s ta tio n
W o rk s ta tio n
T o k e n -rin g
W o rk s ta tio n
To route, the router needs to perform the following :
-
read the destination address Check the possible routes Selects the best route Maintain the Route Table by learning destinations that are not directly connected
CISCO router introduction
What is Routing ? (cont.1) y Observation : Data Link / Physical layers and the Transport/ network layers provide both a mean for conveying data from a Source to a destination across a path.
y Difference : Data Link / Physical layers open a communication across a physical path, Transport/ network layers open a communication across a logical or virtual path thru several data links.
y Data Link / Physical layers determine and store needed information for communication in ARP cache
y Transport / network layers determine and store needed information for communication in ROUTE table
CISCO router introduction
How are processed the received framed packets y The Data link identifier in the destination address field of the frame is examined, if it contains the identifier of the router interface or a broadcast identifier, the router takes the frame and passes the enclosed packet to the network layer.
y The network layer examines the destination IP address, if it is the router interface address or all broadcast address, the protocol field of the packet is examined and the data is sent to the appropriate internal router process.
y Any other destination address not directly connected, the router will do a double route table lookup to acquire the correct route.
CISCO router introduction
Route Table Each route entry in the route table must contains 2 items :
y Destination address : network address that the router can reach y A pointer to the destination called Next-hop which is the address of the next router in the path. The router will match the most specific address in the following priority order :
y y y y y y
Host address A subnet A group of subnet A major network (classfull) A group of major network numbers (supernet) A defaut address
CISCO router introduction
Static and Dynamic Routes Static Routes
y Manually entered in the router Dynamic Routes
y Determined automatically by the Routing Protocol
CISCO router introduction
Static Routing internetwork ROUTER 1 needs to reach ROUTER 3 ROUTER 3 needs to reach ROUTER 1 10.1.5.1
RT : Route Table Router 2
Router 1
Router 3
10.1.3.1 10.1.1.1
10.1.6.1
10.1.2.1
Router 4
10.1.4.2
10.1.7.1
10.1.2.2
RT 1 RT 2 Network 10.1.1.0 10.1.2.0 10.1.4.0
Next hop directly connected directly connected 10.1.2.2
10.1.6.2
10.1.4.1
Network Next hop 10.1.4.0 directly connected 10.1.5.0 directly connected 10.1.6.0 directly connected
RT 3 Network 10.1.2.0 10.1.4.0 10.1.5.0 10.1.6.0
Next hop 10.1.4.1 directly connected directly connected directly connected
RT 4
Network Next hop 10.1.6.0 directly connected 10.1.7.0 directly connected
CISCO router introduction
Static Routing configuration Router 1
Router 3 10.1.2.1
Router 2 10.1.4.2 10.1.2.2
10.1.4.1
On Router 1
y IP route 10.1.4.0 255.255.255.0 10.1.2.2 On Router 3
y IP route 10.1.2.0 255.255.255.0 10.1.4.1
CISCO router introduction
Route Table example ( Cisco Router) •Router 31# show ip route •Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP •
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
•
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
•
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
•
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
•
U - per-user static route, o - ODR
• •Gateway of last resort is not set • •10.0.0.0 is subnetted, 7 subnets
y y y y
•S
10.1.3.0 [1/ 0] via 10.1.4.1
•S
10.1.2.0 [1/ 0] via 10.1.4.1,
•S
10.1.1.0 [1/ 0] via 10.1.4.1,
•S
10.1.7.0 [1/ 0] via 10.1.4.1,
•C
10.1.6.0 is directly connected, Serial1
•C
10.1.5.0 is directly connected, Ethernet0
•C
10.1.4.0 is directly connected, Serial0
[administrative distance / Metric] = [1/0] AD=0 (connected), AD=1(static), AD=100(IGRP),AD=110(OSPF), AD=120 (RIP) The lower the AD, the more believable the protocol Each protocol uses its own metric scheme to define the best route
CISCO router introduction
Exercise 3 : internetwork and route table 10.1.5.1
RT : Route Table Router 2
Router 1
Router 3
10.1.3.1 10.1.1.1
10.1.6.1
10.1.2.1
Router 4
10.1.4.2
10.1.7.1
10.1.2.2
RT 1 RT 2 Network 10.1.1.0 10.1.2.0
Next hop directly connected directly connected
10.1.6.2
10.1.4.1
Network Next hop 10.1.4.0 directly connected 10.1.5.0 directly connected 10.1.6.0 directly connected
RT 3 Network 10.1.4.0 10.1.5.0 10.1.6.0
Next hop directly connected directly connected directly connected
RT 4
Network Next hop 10.1.6.0 directly connected 10.1.7.0 directly connected
On all Routers
y write all pointers to the destinations in NEXT HOP column
CISCO router introduction
Exercise 3 : Result 10.1.5.1
Router 2
Router 1
Router 3
10.1.3.1 10.1.1.1
10.1.6.1
10.1.2.1
Router 4
10.1.4.2
10.1.7.1
10.1.2.2
RT 1 Network 10.1.1.0 10.1.2.0 10.1.3.0 10.1.4.0 10.1.5.0 10.1.6.0 10.1.7.0
Next hop directly connected directly connected 10.1.2.2 10.1.2.2 10.1.2.2 10.1.2.2 10.1.2.2
10.1.6.2
10.1.4.1
RT 2 Network Next hop 10.1.1.0 Not in RT 10.1.2.0 directly connected 10.1.3.0 directly connected 10.1.4.0 directly connected 10.1.5.0 10.1.4.2 10.1.6.0 10.1.4.2 10.1.4.2 10.1.7.0
RT 3 Network 10.1.1.0 10.1.2.0 10.1.3.0 10.1.4.0 10.1.5.0 10.1.6.0 10.1.7.0
Next hop 10.1.4.1 10.1.4.1 10.1.4.1 directly connected directly connected directly connected 10.1.6.2
RT 4 Network Next hop 10.1.1.0 10.1.6.1 10.1.2.0 10.1.6.1 10.1.3.0 10.1.6.1 10.1.4.0 10.1.6.1 10.1.5.0 10.1.6.1 10.1.6.0 directly connected 10.1.7.0 directly connected
On Router 2
y What happens if next hop is missing for network 10.1.1.0 y Every router must have consistent information for correct packet routing
CISCO router introduction
Route table lookup for packet flow 1 0 .1 .5 .1
R o u te r 2
R o u te r 1
R o u te r 3
1 0 .1 .3 .1 1 0 .1 .1 .1
1 0 .1 .6 .1
1 0 .1 .2 .1
R o u te r 4
1 0 .1 .4 .2
1 0 .1 .7 .1
1 0 .1 .2 .2
N e tw o rk 1 0 .1 .1 .0 1 0 .1 .2 .0 1 0 .1 .3 .0 1 0 .1 .4 .0 1 0 .1 .5 .0 1 0 .1 .6 .0 1 0 .1 .7 .0
N ext hop d ir e c tly c o n n e c te d d ir e c tly c o n n e c te d 1 0 .1 .2 .2 1 0 .1 .2 .2 1 0 .1 .2 .2 1 0 .1 .2 .2 1 0 .1 .2 .2
1 0 .1 .6 .2
1 0 .1 .4 .1
RT 1 RT 2 N e tw o rk 1 0 .1 .1 .0 1 0 .1 .2 .0 1 0 .1 .3 .0 1 0 .1 .4 .0 1 0 .1 .5 .0 1 0 .1 .6 .0 1 0 .1 .7 .0
N ext hop N o t in R T d ir e c tly c o n n e c te d d ir e c tly c o n n e c te d d ir e c tly c o n n e c te d 1 0 .1 .4 .2 1 0 .1 .4 .2 1 0 .1 .4 .2
RT 3 N e tw o rk 1 0 .1 .1 .0 1 0 .1 .2 .0 1 0 .1 .3 .0 1 0 .1 .4 .0 1 0 .1 .5 .0 1 0 .1 .6 .0 1 0 .1 .7 .0
N ext hop 1 0 .1 .4 .1 1 0 .1 .4 .1 1 0 .1 .4 .1 d ir e c tly c o n n e c te d d ir e c tly c o n n e c te d d ir e c tly c o n n e c te d 1 0 .1 .6 .2
RT 4 N e tw o rk Next hop 1 0 .1 .1 .0 1 0 .1 .6 .1 1 0 .1 .2 .0 1 0 .1 .6 .1 1 0 .1 .3 .0 1 0 .1 .6 .1 1 0 .1 .4 .0 1 0 .1 .6 .1 1 0 .1 .5 .0 1 0 .1 .6 .1 1 0 .1 .6 .0 d ir e c t ly c o n n e c te d 1 0 .1 .7 .0 d ir e c t ly c o n n e c te d
y Router 1 receives a packet with a source address of 10.1.1.97 and a destination address of 10.1.7.10
y Route table lookup find 10.1.7.0 subnet as best match reachable via next-hop address 10.1.2.2 on interface S0
y The packet is sent to that next router (Router 2) y Process continues until packet reaches Router 4 which sees that the destination is on Directly connected subnet 10.1.7.0
CISCO router introduction
Case Study 1 :Simple Static routes Router 2 192.168.1.1 / 27
192.168.1.65 / 27
192.168.1.193 / 27
Router 4 10.1.5.1 / 16
192.168.1.66 / 27
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.6.1 / 24
10.4.7.1 / 24
Router 3
y The subnets of network 10.0.0.0 are discontiguous, a major network subnet separates 10.1.0.0 from other 10.0.0.0 subnets
y The subnets of 10.0.0.0 are also variably subnetted, the subnet mask are not consistent thru the major intermediate network
y This will not work with classfull routing protocol (RIP V1, IGRP) y Static routes work fine, Variable Length Subnet Masking (VLSM) is also useful.
CISCO router introduction
3 steps : Simple Static route configuration Router 2 192.168.1.1 / 27
192.168.1.65 / 27
192.168.1.193 / 27
Router 4 10.1.5.1 / 16
192.168.1.66 / 27
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.6.1 / 24
10.4.7.1 / 24
Router 3
1. 2. 3.
For each link determine the subnet or network address For each router identify all links not directly connected For each router write a route statement for each link not directly connected
CISCO router introduction
Step 1 : Simple Static route configuration Router 2 192.168.1.1 / 27
192.168.1.65 / 27
192.168.1.193 / 27
Router 4 10.1.5.1 / 16
192.168.1.66 / 27
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.6.1 / 24
The internetwork has six subnets
y 10.1.0.0 / 16 y 10.4.6.0 / 24 y10.4.7.0 / 24 y192.168.1.192 / 27 y192.168.1.64 / 27 y192.168.1.0 / 27
10.4.7.1 / 24
Router 3
CISCO router introduction
Step 2 : Simple Static route configuration Router 2 192.168.1.1 / 27
192.168.1.65 / 27
192.168.1.193 / 27
Router 4 10.1.5.1 / 16
192.168.1.66 / 27
10.4.6.2 / 24
Router 1 Router 1 :
192.168.1.194 / 27 10.4.6.1 / 24
Router 4 :
Subnets not directly connected
y 10.1.0.0 / 16 y10.4.6.0 / 24 y10.4.7.0 / 24 y192.168.1.192 / 27
10.4.7.1 / 24
Router 3
Subnets not directly connected
y10.4.6.0 / 24 y10.4.7.0 / 24 y192.168.1.64 / 27 y192.168.1.0 / 27
CISCO router introduction
Step 3 : Simple Static route configuration (cont.1) R o u te r 2
1 9 2 .1 6 8 .1 .1 / 2 7
1 9 2 .1 6 8 .1 .6 5 / 2 7
R o u te r 4
1 9 2 .1 6 8 .1 .1 9 3 / 2 7
1 0 .1 .5 .1 / 1 6 1 9 2 .1 6 8 .1 .6 6 / 2 7
1 0 .4 .6 .2 / 2 4
R o u te r 1
1 9 2 .1 6 8 .1 .1 9 4 / 2 7 1 0 .4 .6 .1 / 2 4
1 0 .4 .7 .1 / 2 4
R o u te r 3
y Router1 (confg)# ip route 192.168.1.192 255.255.255.224 192.1.168.1.66 y Router1 (confg)# ip route 10.1.0.0 255.255.0.0 192.1.168.1.66 y Router1 (confg)# ip route 10.4.6.0 255.255.0.0 192.1.168.1.66 y Router1 (confg)# ip route 10.4.7.0 255.255.0.0 192.1.168.1.66 y Router 2 (confg)# ip route 192.168.1.0 255.255.255.224 192.168.1.65 y Router 2 (confg)# ip route 10.1.0.0 255.255.0.0 192.1.168.194 y Router 2 (confg)# ip route 10.4.7.0 255.255.255.0 10.4.6.1
CISCO router introduction
Step 3 : Simple Static route configuration R o u te r 2 (cont.2) 1 9 2 .1 6 8 .1 .1 / 2 7
1 9 2 .1 6 8 .1 .6 5 / 2 7
R o u te r 4
1 9 2 .1 6 8 .1 .1 9 3 / 2 7
1 0 .1 .5 .1 / 1 6 1 9 2 .1 6 8 .1 .6 6 / 2 7
1 0 .4 .6 .2 / 2 4
R o u te r 1
1 9 2 .1 6 8 .1 .1 9 4 / 2 7 1 0 .4 .6 .1 / 2 4
1 0 .4 .7 .1 / 2 4
R o u te r 3
y Router3 (confg)# ip route 192.168.1. 0 255.255.255.224 10.4.6.2 y Router3 (confg)# ip route 192.168.1. 64 255.255.255.224 10.4.6.2 y Router3 (confg)# ip route 192.168.1. 192 255.255.255.224 10.4.6.2 y Router3 (confg)# ip route 10.1.0.0 255.255.0.0 10.4.6.2 y Router 4 (confg)# ip route 192.168.1.0 255.255.255.224 192.168.1.193 y Router 4 (confg)# ip route 192.168.1.64 255.255.255.224 192.168.1.193 y Router 4 (confg)# ip route 10.4.6.0 255.255.255.0 192.168.1.193 y Router 4 (confg)# ip route 10.4.7.0 255.255.255.0 192.168.1.193
CISCO router introduction
Case Study 2 : Summary routes (1) R o u te r 2 1 9 2 .1 6 8 .1 .1 / 2 7
1 9 2 .1 6 8 .1 .6 5 / 2 7
R o u te r 4
1 9 2 .1 6 8 .1 .1 9 3 / 2 7
1 0 .1 .5 .1 / 1 6 1 9 2 .1 6 8 .1 .6 6 / 2 7
1 0 .4 .6 .2 / 2 4
R o u te r 1
1 9 2 .1 6 8 .1 .1 9 4 / 2 7 1 0 .4 .6 .1 / 2 4
1 0 .4 .7 .1 / 2 4
R o u te r 3
Subnets 10.4.6.0/24 and 10.4.7.0/24 could be specified to Router4 with a single entry 10.4.0.0/16 Subnets 192.168.1.0/27 and 192.168.1.64/27 could be specified to Router4 with a single entry 192.168.1.0/24
y Router 4 (confg)# ip route 192.168.1.0 255.255.255.0 192.168.1.193 y Router 4 (confg)# ip route 10.4.0.0 255.255.0.0 192.168.1.193 Frpm Router 1 via Rouer 2 all subnets of network 10.0.0.0 are reachable , so a single entry to that major network is needed
y Router 1 (confg)# ip route 192.168.1.192 255.255.255.224 192.168.1.66 y Router 1 (confg)# ip route 10.0.0.0 255.0.0.0 192.168.1.66
CISCO router introduction
Case Study 2 : Summary routes (2) R o u te r 2 1 9 2 .1 6 8 .1 .1 / 2 7
1 9 2 .1 6 8 .1 .6 5 / 2 7
R o u te r 4
1 9 2 .1 6 8 .1 .1 9 3 / 2 7
1 0 .1 .5 .1 / 1 6 1 9 2 .1 6 8 .1 .6 6 / 2 7
1 0 .4 .6 .2 / 2 4
R o u te r 1
1 9 2 .1 6 8 .1 .1 9 4 / 2 7 1 0 .4 .6 .1 / 2 4
1 0 .4 .7 .1 / 2 4
R o u te r 3 Frpm Router 3 via Rouer 2 all subnets of network 192.0.0.0 are reachable , so a single entry to that major network is needed
y Router 1 (confg)# ip route 192.0.0.0 255.0.0.0 10.4.6.1 y Router 1 (confg)# ip route 10.1.0.0 255.255.0.0 10.4.6.1 Caution must be taken with simmarization to avoid unexpected routing behavior
CISCO router introduction
Case Study 3 : Floating static routes (1) Router 2 192.168.1.1 / 27
192.168.1.65 / 27
192.168.1.193 / 27
Router 4 10.1.5.1 / 16
192.168.1.66 / 27 10.4.8.2 / 24
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.8.1 / 24
10.4.6.1 / 24
10.4.7.1 / 24
Router 3 y Static route is not permanently in Route Table y Appears only when preferred route fails y Administrative distance is added to static route y The router selects as primary the route with lower Administrative distance
CISCO router introduction
Case Study 3 : Floating static routes (2) Router 2 192.168.1.1 / 27
192.168.1.65 / 27
Router 4
192.168.1.193 / 27
10.1.5.1 / 16 192.168.1.66 / 27 10.4.8.2 / 24
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.8.1 / 24
10.4.6.1 / 24
10.4.7.1 / 24
Router 3 y y y y y y y y
Router3 (confg)# ip route 192.168.1. 0 255.255.255.224 10.4.6.2 Router3 (confg)# ip route 192.168.1. 64 255.255.255.224 10.4.6.2 Router3 (confg)# ip route 192.168.1. 192 255.255.255.224 10.4.6.2 Router3 (confg)# ip route 10.1.0.0 255.255.0.0 10.4.6.2 Router3 (confg)# ip route 192.168.1. 0 255.255.255.224 10.4.6.2 10 Router3 (confg)# ip route 192.168.1. 64 255.255.255.224 10.4.6.2 10 Router3 (confg)# ip route 192.168.1. 192 255.255.255.224 10.4.6.2 10 Router3 (confg)# ip route 10.1.0.0 255.255.0.0 10.4.6.2 10
CISCO router introduction
Case Study 3 : Floating static routes (3) Router 2 192.168.1.1 / 27
192.168.1.65 / 27
Router 4
192.168.1.193 / 27
10.1.5.1 / 16 192.168.1.66 / 27 10.4.8.2 / 24
10.4.6.2 / 24
Router 1
192.168.1.194 / 27 10.4.8.1 / 24
10.4.6.1 / 24
10.4.7.1 / 24
Router 3
y Router 2 (confg)# ip route 10.4.7.0 255.255.255.0 10.4.6.1 y Router 2 (confg)# ip route 10.4.7.0 255.255.255.0 10.4.6.1 10
