understanding the routing table part 1: the routing table structure part 2: the lookup process rick...
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Understanding The Routing Table
Part 1: The Routing Table Structure
Part 2: The Lookup Process
Rick Graziani
Cabrillo College
Rick Graziani [email protected] 2
The Routing Table on PDF
• Instructors and Students: Complete information explanations associated with this PowerPoint can be found on my web site.
Understanding the Routing Table
• The Routing Table: Part 1 or 2 - The Routing Table Structure (PDF)
• The Routing Table: Part 2 or 2 - The Routing Table Lookup Process (PDF)
• Discard Routes - Avoiding Routing Loops (PowerPoint)
Part 1: The Routing Table Structure
Rick Graziani [email protected] 4
Directly Connected Networks
RouterB#show ip routeCodes: 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, ia - IS-IS inter
area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set RouterB#
Router B Router CRouter A
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
Rick Graziani [email protected] 5
Directly Connected Networks
RouterB#debug ip routing
RouterB(config)#interface s 1
RouterB(config-if)#ip add 192.168.1.1 255.255.255.0
RouterB(config-if)#no shutdown
00:59:48: %LINK-3-UPDOWN: Interface Serial1, changed state to up
00:59:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed state
to up
00:59:48: RT: add 192.168.1.0/24 via 0.0.0.0, connected metric [0/0]
00:59:48: RT: interface Serial1 added to routing table
RouterB(config-if)#end
RouterB#undebug all
All possible debugging has been turned off
RouterB#
Rick Graziani [email protected] 6
Directly Connected Networks
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
C 192.168.1.0/24 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 7
Creating a Parent/Child Route
RouterB(config)#interface fastethernet 0RouterB(config-if)#ip add 172.16.3.1 255.255.255.0RouterB(config-if)#no shutdown01:21:11: RT: add 172.16.3.0/24 via 0.0.0.0, connected metric [0/0]01:21:11: RT: interface FastEthernet0 added to routing tableRouterB(config-if)#endRouterB#undebug allAll possible debugging has been turned offRouterB#RouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile,<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 1 subnetsC 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1RouterB#
Rick Graziani [email protected] 8
Parent, Child, Ultimate Routes
So far on Router B:
Parent Route: 172.16.0.0/24 is subnetted, 1 subnets
Child Route: C 172.16.3.0 is directly connected, FastEthernet0
Ultimate Route: C 192.168.1.0/24 is directly connected, Serial1
Router B Router CRouter A
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
Rick Graziani [email protected] 9
Creating Another Child Route
RouterB(config)#inter s 0
RouterB(config-if)#ip add 172.16.2.2 255.255.255.0
RouterB(config-if)#end
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 10
Same structure no matter the source of route
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 4 subnets
S 172.16.4.0 is directly connected, Serial1
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:08, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
10.0.0.0/16 is subnetted, 1 subnets
S 10.1.0.0 is directly connected, Serial1
C 192.168.1.0/24 is directly connected, Serial1
S 192.168.100.0/24 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 11
Static Routes and Recursive Lookups
RouterA#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 2 subnetsC 172.16.1.0 is directly connected, FastEthernet0C 172.16.2.0 is directly connected, Serial0RouterA#RouterA(config)#ip route 172.16.3.0 255.255.255.0 172.16.2.203:12:45: RT: add 172.16.3.0/24 via 172.16.2.2, static metric [1/0]RouterA(config)#
Router B Router CRouter A
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
Rick Graziani [email protected] 12
Static Routes and Recursive Lookups
RouterA#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 3 subnets
C 172.16.1.0 is directly connected, FastEthernet0
C 172.16.2.0 is directly connected, Serial0
S 172.16.3.0 [1/0] via 172.16.2.2
RouterA#
First lookup of 172.16.3.0:
S 172.16.3.0 [1/0] via 172.16.2.2
Second lookup of 172.16.2.0:
C 172.16.2.0 is directly connected, Serial0
Rick Graziani [email protected] 13
Static Routes without Recursive Lookup
RouterB(config)#ip route 172.16.1.0 255.255.255.0 serial 005:05:30: RT: add 172.16.1.0/24 via 0.0.0.0, static metric [1/0]RouterB(config)#RouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnetsS 172.16.1.0 is directly connected, Serial0C 172.16.2.0 is directly connected, Serial0C 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1RouterB#
Router B Router CRouter A
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
Rick Graziani [email protected] 14
Static Routes and Administrative Distance
You might have also noticed that the routing table states that this static route is “directly connected.”
S 172.16.1.0 is directly connected, Serial0
• In the case of a static route, directly connected means that the static route was configured with an exit interface.
• This does not mean that it is a directly connected network like an interface on the router.
• Like all static routes, the default administrative distance of this static route is still “1”.
• Only directly connected interfaces, (which have a code of “C” in the routing table) can have an administrative distance of “0”.
• Although it is possible to modify the administrative distance of static and dynamic routes, they cannot be given the administrative distance of “0”.
• Likewise, directly connected interfaces can only have an administrative distance of “0”.
Rick Graziani [email protected] 15
Static Routes via Ethernet Interfaces
RouterB(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1RouterB(config)#end RouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnetsS 172.16.1.0/24 [1/0] via 172.16.2.1 C 172.16.2.0 is directly connected, FastEthernet1C 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1RouterB#
Router B Router CRouter A
fa1 fa1 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
Rick Graziani [email protected] 16
Static Routes via Ethernet Interfaces
RouterB(config)#ip route 172.16.1.0 255.255.255.0 fastethernet 1 172.16.2.1
RouterB(config)#end
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 3 subnets
S 172.16.1.0/24 [1/0] via 172.16.2.1 FastEthernet1
C 172.16.2.0 is directly connected, FastEthernet1
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 17
VLSM
RouterX#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.1.4/30 is directly connected, Serial0
C 172.16.1.8/30 is directly connected, Serial1
C 172.16.3.0/24 is directly connected, FastEthernet0
RouterX#
Router X
s0 s1
fa0172.16.1.4/30
172.16.3.0/24
.5
.1
.9172.16.1.8/30
Part 2: The Lookup Process
Rick Graziani [email protected] 19
Subnet Mask = # of bits that must match
RouterA#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, FastEthernet0C 172.16.2.0 is directly connected, Serial0R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:00, Serial0R 192.168.1.0/24 [120/1] via 172.16.2.2, 00:00:00, Serial0RouterA#
Figure 2 IP Packet
192.168.1.10 11000000
10101000
00000001
00001010
16 bits must match, but only one bit matches.
Parent Route
172.16.0.0
10101100
00010000
00000000
00000000
Rick Graziani [email protected] 20
Subnet Mask = # of bits that must match
RouterA#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 3 subnets
C 172.16.1.0 is directly connected, FastEthernet0
C 172.16.2.0 is directly connected, Serial0
R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:00, Serial0
R 192.168.1.0/24 [120/1] via 172.16.2.2, 00:00:00, Serial0
RouterA#
Figure 3 IP Packet
192.168.1.10
11000000
10101000
00000001
00001010
These 24 bits match!
Ultimate Route
192.168.1.0
11000000
10101000
00000001
00000000
Rick Graziani [email protected] 21
Parent then Children
RouterA#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, FastEthernet0C 172.16.2.0 is directly connected, Serial0R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:00, Serial0R 192.168.1.0/24 [120/1] via 172.16.2.2, 00:00:00, Serial0RouterA#
IP Packet
172.16.3.10
10101100
00010000
00000011
00001010
These 16 bits match!
Parent Route
172.16.0.0
10101100
00010000
00000000
00000000
Rick Graziani [email protected] 22
RouterA#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<text omitted> Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, FastEthernet0C 172.16.2.0 is directly connected, Serial0R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:00, Serial0R 192.168.1.0/24 [120/1] via 172.16.2.2, 00:00:00, Serial0RouterA#
Figure 6 (child routes shown in different order than with ‘show ip route’) IP Packet
172.16.3.10
10101100
00010000
00000011
00001010
These 24 bits match!
Child Route
172.16.3.0
10101100
00010000
00000011
00000000
Child Route
172.16.1.0
10101100
00010000
00000001
00000000
Child Route
172.16.2.0
10101100
00010000
00000010
00000000
Rick Graziani [email protected] 23
The Default Route
RouterB(config)#ip route 0.0.0.0 0.0.0.0 serial1
RouterB(config)#end
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:13, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 24
Classful Routing Behavior
RouterB#show running-config
Building configuration...
Current configuration:
!
version 11.2
!
<text omitted>
!
no ip classless
!
<text omitted>
Rick Graziani [email protected] 25
Classful Routing Behavior
RouterB#show ip routeGateway of last resort is 0.0.0.0 to network 0.0.0.0 172.16.0.0/24 is subnetted, 3 subnetsR 172.16.1.0 [120/1] via 172.16.2.1, 00:00:13, Serial0C 172.16.2.0 is directly connected, Serial0C 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1S* 0.0.0.0/0 is directly connected, Serial1RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
No match!
Child Route
172.16.3.0
10101100
00010000
00000011
00000000
Child Route
172.16.1.0
10101100
00010000
00000001
00000000
Child Route
172.16.2.0
10101100
00010000
00000010
00000000
Rick Graziani [email protected] 26
Classful Routing Behavior
Routing Behavior: classful (no ip classless)
Packet’s Destination IP Address: 172.16.4.10
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP,
<text omitted>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
1. Match 172.16.0.0/24 is subnetted, 3 subnets
2. No Match R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:13, Serial0
3. No Match C 172.16.2.0 is directly connected, Serial0
4. No Match C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
5. Drop Packet S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 27
Classless Routing Behavior
RouterB#show running-config
Building configuration...
Current configuration:
!
version 11.3
!
<text omitted>
!
ip classless
!
<text omitted>
Rick Graziani [email protected] 28
Classless Routing Behavior
RouterB#show ip routeGateway of last resort is 0.0.0.0 to network 0.0.0.0 172.16.0.0/24 is subnetted, 3 subnetsR 172.16.1.0 [120/1] via 172.16.2.1, 00:00:13, Serial0C 172.16.2.0 is directly connected, Serial0C 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1S* 0.0.0.0/0 is directly connected, Serial1RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
No match!
Child Route
172.16.3.0
10101100
00010000
00000011
00000000
Child Route
172.16.1.0
10101100
00010000
00000001
00000000
Child Route
172.16.2.0
10101100
00010000
00000010
00000000
Rick Graziani [email protected] 29
Classless Routing Behavior
Routing Behavior: classless (ip classless)
Packet’s Destination IP Address: 172.16.4.10
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP,
<text omitted>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
1. Match 172.16.0.0/24 is subnetted, 3 subnets
2. No Match R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:13, Serial0
3. No Match C 172.16.2.0 is directly connected, Serial0
4. No Match C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
5. Match! S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 30
Classless and Classful Routing Behavior
Changing the default routing behavior, whether classful or classless, is simple. The command to enable classless routing behavior is:
RouterB(config)#ip classless
RouterB(config)#
The command to disable classless routing behavior, in other words, enable classful routing behavior is:
RouterB(config)#no ip classless
RouterB(config)#
Use show running-config to verify which command is in affect.
Rick Graziani [email protected] 31
/16 Classful Routes
RouterC(config)#interface loopback1
RouterC(config-if)#ip add 172.20.0.1 255.255.0.0
RouterC(config-if)#exit
RouterC(config)#interface loopback2
RouterC(config-if)#ip add 172.30.0.1 255.255.0.0
RouterC(config-if)#exit
RouterC#show ip inter brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 172.16.4.1 YES NVRAM up up
Loopback1 172.20.0.1 YES manual up up
Loopback2 172.30.0.1 YES manual up up
Serial0 192.168.1.2 YES NVRAM up up
RouterC#
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
172.16.10.0/24 lo1
172.16.20.0/24 lo2
172.16.30.0/24 lo3
172.16.40.0/24 lo4
Rick Graziani [email protected] 32
/16 Classful Routes
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 6 subnets, 2 masks
C 172.16.4.0/24 is directly connected, FastEthernet0
S 172.16.0.0/16 is directly connected, Serial0
C 172.20.0.0/16 is directly connected, Loopback1
C 172.30.0.0/16 is directly connected, Loopback2
C 192.168.1.0/24 is directly connected, Serial0
RouterC#
s0 s0 s0s1
fa0 fa0 fa0
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24 172.16.4.0/24
192.168.1.0/24.1
.1 .2
.1
.1
.1
.2
172.16.10.0/24 lo1
172.16.20.0/24 lo2
172.16.30.0/24 lo3
172.16.40.0/24 lo4
Rick Graziani [email protected] 33
Static Routes to Supernets
RouterB(config)#ip route 172.0.0.0 255.0.0.0 serial1
RouterB(config)#ip route 160.0.0.0 240.0.0.0 serial1
RouterB(config)#end
RouterB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<text omitted>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:20, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
S 172.0.0.0/8 is directly connected, Serial1
S 160.0.0.0/4 is directly connected, Serial1
S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
Rick Graziani [email protected] 34
Supernets
RouterB#show ip route
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:20, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
S 172.0.0.0/8 is directly connected, Serial1
S 160.0.0.0/4 is directly connected, Serial1
S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
No match!
Child Route
172.16.3.0
10101100
00010000
00000011
00000000
Child Route
172.16.1.0
10101100
00010000
00000001
00000000
Child Route
172.16.2.0
10101100
00010000
00000010
00000000
Rick Graziani [email protected] 35
Supernets – 172.0.0.0 best match
RouterB#show ip route 172.16.0.0/24 is subnetted, 3 subnetsR 172.16.1.0 [120/1] via 172.16.2.1, 00:00:20, Serial0C 172.16.2.0 is directly connected, Serial0C 172.16.3.0 is directly connected, FastEthernet0C 192.168.1.0/24 is directly connected, Serial1S 172.0.0.0/8 is directly connected, Serial1S 160.0.0.0/4 is directly connected, Serial1S* 0.0.0.0/0 is directly connected, Serial1RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
Longest-bit-match! (11 bits match, 8 bits minimum)
Supernet
172.0.0.0/8
10101100
00000000
00000000
00000000
Supernet
160.0.0.0/4
10100000
00000000
00000000
00000000
Default
0.0.0.0/0
00000000
00000000
00000000
00000000
Rick Graziani [email protected] 36
Supernets – 160.0.0.0 best match
RouterB#show ip route
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:20, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
S 160.0.0.0/4 is directly connected, Serial1
S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
Longest-bit-match! (4 bits)
Supernet
160.0.0.0/4
10100000
00000000
00000000
00000000
Default
0.0.0.0/0
00000000
00000000
00000000
00000000
Rick Graziani [email protected] 37
The last of the Supernets – 0.0.0.0/0
RouterB#show ip route
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.1.0 [120/1] via 172.16.2.1, 00:00:20, Serial0
C 172.16.2.0 is directly connected, Serial0
C 172.16.3.0 is directly connected, FastEthernet0
C 192.168.1.0/24 is directly connected, Serial1
S* 0.0.0.0/0 is directly connected, Serial1
RouterB#
IP Packet
172.16.4.10
10101100
00010000
00000100
00001010
Match! Zero bits needed to match, which still makes it a
match! Default
0.0.0.0/0
00000000
00000000
00000000
00000000
Rick Graziani [email protected] 38
The Routing Table on PDF
• Complete information explanations associated with this PowerPoint can be found on my web site.
Understanding the Routing Table
• The Routing Table: Part 1 or 2 - The Routing Table Structure (PDF)
• The Routing Table: Part 2 or 2 - The Routing Table Lookup Process (PDF)
• Discard Routes - Avoiding Routing Loops (PowerPoint)