Transcript Routes - Chabot College

Chabot College
ELEC 99.08
IP Routing Protocol Highlights
CISCO NETWORKING ACADEMY
IP Routing Protocol Topics
•
•
•
•
•
•
•
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Routing tables
How routes are learned
Default routes
Metrics
Administrative Distance
Distance Vector / Link State
RIP / IGRP
Commands
CISCO NETWORKING ACADEMY
Routing Table
• Stored in RAM
• Basis for all path selection decisions
• Includes
destination network address - next hop pairs
CISCO NETWORKING ACADEMY
Routing Table Example
hayward#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP
D - EIGRP, EX - EIGRP external, O - OSPF
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, * - candidate default
Gateway of last resort is not set
R
C
C
R
R
S
C
192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
10.2.0.0 is directly connected, Serial1
10.3.0.0 is directly connected, Serial0
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
192.168.2.0/24 [1/0] via 10.2.0.1
192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
Routing Table Example
hayward#show ip route
Destination Network Address
R
C
C
R
R
S
C
Next Hop
192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
10.2.0.0 is directly connected, Serial1
10.3.0.0 is directly connected, Serial0
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
192.168.2.0/24 [1/0] via 10.2.0.1
192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
How routes are learned
1. Interface configuration in the config file.
Defines directly connected networks even
when no dynamic routing is configured:
hayward#show ip route
10.0.0.0/16 is subnetted
C
10.2.0.0 is directly connected, Serial1
C
10.3.0.0 is directly connected, Serial0
C 192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
How routes are learned
When dynamic routing is running, directly
connected networks are listed in the routing
table along with others:
hayward#show ip route
R 192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
C
10.2.0.0 is directly connected, Serial1
C
10.3.0.0 is directly connected, Serial0
R
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
R 192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
S 192.168.2.0/24 [1/0] via 10.2.0.1
C 192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
How routes are learned
2. Static routes entered manually in the router
config file.
hayward#show ip route
R 192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
C
10.2.0.0 is directly connected, Serial1
C
10.3.0.0 is directly connected, Serial0
R
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
R 192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
S 192.168.2.0/24 [1/0] via 10.2.0.1
C 192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
How routes are learned
3. Routes learned from a dynamic routing
protocol (e.g. RIP, IGRP, OSPF).
hayward#show ip route
R 192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
C
10.2.0.0 is directly connected, Serial1
C
10.3.0.0 is directly connected, Serial0
R
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
R 192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
S 192.168.2.0/24 [1/0] via 10.2.0.1
C 192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
How routes are learned
4. Default route set manually.
Shown with *
Also: gateway of last resort
oakland#show ip route
Gateway of last resort is 10.2.0.1 to network 0.0.0.0
10.0.0.0/16 is subnetted, 2 subnets
C
10.2.0.0 is directly connected, Serial1
R
10.1.0.0 [120/1] via 10.2.0.1, 00:00:18, Serial1
R 192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:18, Serial1
S 192.168.2.0/24 [1/0] via 10.2.0.1
C 192.168.3.0/24 is directly connected, Ethernet0
R* 0.0.0.0/0 [1/0] via 10.2.0.1
CISCO NETWORKING ACADEMY
Static Routes - Why?
• Security
– RIP may reveal too much of your network to others.
A static route limits what you “show”.
• Backup routes
– A static route can be a backup to be used
automatically if a dynamic route goes down
• Bandwidth conservation
– Dynamic routing uses network bandwidth; static
routes do not.
– Static routes are sufficient for stub networks
CISCO NETWORKING ACADEMY
Stub Networks
• Only one path in & out of the network;
no path selection decision:
Only one path to this “stub” network
A static route
to the stub net
will do.
Here, there are path selection decisions.
Dynamic routing needed.
CISCO NETWORKING ACADEMY
Default Routes - the Problem
• For each packet, routing are decisions based on
the routing table rules.
• What happens to a packet if has a destination
that is not included in the routing table?
CISCO NETWORKING ACADEMY
Default Routes - the Problem
• What happens to a packet sent to 209.33.45.177
• It is dropped because there is no entry for that
network in the routing table:
oak#show ip route
Gateway of last resort is not set
R
C
C
R
R
S
C
192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:07, Serial0
10.0.0.0/16 is subnetted, 3 subnets
10.2.0.0 is directly connected, Serial1
10.3.0.0 is directly connected, Serial0
10.1.0.0 [120/1] via 10.2.0.1, 00:00:10, Serial1
192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:10, Serial1
192.168.2.0/24 [1/0] via 10.2.0.1
192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
Default Routes - the Problem
• But the routing table can’t hold entries for every
network, including all those on the Internet!
• So we need a route for internet traffic - the
default.
Gateway
Our Network
If packet has a destination
not on our network,
try sending it here
CISCO NETWORKING ACADEMY
Default Routes - Terms
• default route
(through)
• default gateway
(also known as)
• gateway of last resort
(to)
• default network
CISCO NETWORKING ACADEMY
Metric
• Specifies the cost of a route
• Dynamic routing protocol chooses the route with
the lowest cost
• Metrics differ, depending on routing protocol:
Protocol
Metric
RIP
Hop Count
(# routers packet must pass through)
Default: Bandwidth, Delay
Optionally include: [Load, Reliability]
IGRP
CISCO NETWORKING ACADEMY
Administrative Distance
• Specifies the trustworthiness of a route source
• 0 - 255 Lower values = more trustworthy
• The IOS chooses the route with lowest distance:
IOS ignores these routes
CISCO NETWORKING ACADEMY
Route Source
Default Distance
Connected interface
Static Route
EIGRP Summary Route
External BGP
Internal EIGRP
IGRP
OSPF
IS-IS
RIP
EGP
Internal BGP
Unknown
0
1
5
20
90
100
110
115
120
140
200
255
Distance Vector vs Link State
• Distance Vector
– Each router knows:
• Direction (vector)
• Distance (hops)
– Example. Destination is:
• out S0
• 3 hops away
– Does not know exact map to destination.
3 hops
CISCO NETWORKING ACADEMY
Distance Vector vs Link State
• Distance Vector
– To reach Joe’s office:
Go out middle door & pass through 3 buildings.
At each building, you’ll be told which door to exit
– Which office could be Joe’s?
3
CISCO NETWORKING ACADEMY
Distance Vector vs Link State
• Distance Vector
– To reach Joe’s office:
Go out middle door & pass through 3 buildings.
At each building, you’ll be told which door to exit
– Which office could be Joe’s?
3
CISCO NETWORKING ACADEMY
2
Distance Vector vs Link State
• Distance Vector
– To reach Joe’s office:
Go out middle door & pass through 3 buildings.
At each building, you’ll be told which door to exit
– Which office could be Joe’s?
3
2
1
CISCO NETWORKING ACADEMY
Distance Vector vs Link State
• Distance Vector
– To reach Joe’s office:
Go out middle door & pass through 3 buildings.
At each building, you’ll be told which door to exit
– Which office could be Joe’s?
3
2
1
CISCO NETWORKING ACADEMY
0
Distance Vector vs Link State
• Distance Vector
– To reach Joe’s office:
Go out middle door & pass through 3 buildings.
At each building, you’ll be told which door to exit
– Which office could be Joe’s?
3
2
1
CISCO NETWORKING ACADEMY
0
Joe
Distance Vector vs Link State
• Link State
– Each router knows:
• Overall map of network
• Shortest path to destination
CISCO NETWORKING ACADEMY
Distance Vector vs Link State
• Link State
– To reach Joe’s office:
Follow Campus Map.
Take shortest path.
Joe
CISCO NETWORKING ACADEMY
Distance Vector vs Link State
• Distance Vector Updates (RIP example)
–
–
–
–
Each router gossips to its direct neighbor.
Gossip is sent every 30 seconds.
Takes time to pass the gossip to the end of the line.
When all routers have received the gossip they are
“converged”. Until then, the routers posses conflicting
knowledge.
A tells B
A
B tells C
B
CISCO NETWORKING ACADEMY
C tells D
C
D tells E
D
E tells F
E
F
Distance Vector vs Link State
• Link State
– Each router sends information about its links to all
other routers.
– Changes in network topology trigger these link state
advertisements.
– Each router then develops a full map of the network.
Down
A tells all other routers when it learns of a change in the network
A
B
C
D
E
When any other router detects a change, it also tells everyone.
CISCO NETWORKING ACADEMY
F
RIP
•
•
•
•
•
•
Distance-Vector
Updates: every 30 seconds
Metric: Hops
Default administrative distance: 120
Convergence: slow
Versions 1 & 2
CISCO NETWORKING ACADEMY
IGRP
• Distance-Vector
• Updates: every 90 seconds
• Metric: bandwidth & delay (defaults)
Can also include load, reliability
• Default administrative distance: 100
• Convergence: faster than RIP
CISCO NETWORKING ACADEMY
Configuring Dynamic Routing
1. Specify the routing protocol.
– Ordinarily, all routers must run the same protocol.
2. Specify all directly connected networks on which
the router will send and receive route updates
(also called advertisements).
– Network are specified by major network numbers, not
subnets. Example - here the network is 10.0.0.0:
10.2.0.2/16
CISCO NETWORKING ACADEMY
10.3.0.1/16
Commands
• Configuring RIP
Sets RIP to send/receive updates on
these directly connected networks
Enables RIP routing
oak(config)#router rip
oak(config-router)#network 10.0.0.0
oak(config-router)#network 192.168.3.0
oak(config-router)#^Z
CISCO NETWORKING ACADEMY
Commands
• Configuring RIP version 2 - same as RIP but
– adds version 2 statement
– version should be the same for all routers
Enables RIP routing
Sets RIP version 2
oak(config)#router rip
oak(config-router)#version 2
oak(config-router)#network 10.0.0.0
oak(config-router)#network 192.168.4.0
oak(config-router)#^Z
CISCO NETWORKING ACADEMY
Commands
• Configuring IGRP - same as RIP, but
– includes an autonomous system number
– AS must be same for all routers
Enables IGRP routing
Autonomous System #
oak(config)#router igrp 40
oak(config-router)#network 10.0.0.0
oak(config-router)#network 192.168.3.0
oak(config-router)#^Z
CISCO NETWORKING ACADEMY
Commands
• Configuring a static route - outgoing interface
Route to network via
this outgoing interface
Destination network & mask
fre(config)#ip route 192.168.1.0 255.255.255.0 s0
fre(config)#^Z
CISCO NETWORKING ACADEMY
Commands
• Configuring a static route - next hop
Destination network & mask
fre(config)#ip route 192.168.1.0 255.255.255.0 s0
fre(config)#ip route 192.168.1.0 255.255.255.0 10.1.0.2
fre(config)#^Z
Route to network via
this next hop address.
Use this format to improve
clarity of routing tables.
CISCO NETWORKING ACADEMY
Comands
• Specifying next hop
– It is the ip address of nearest interface of the neighbor
router along the route.
– From Router B, this is the next hop to LAN A:
B
LAN D
LAN C
LAN A
CISCO NETWORKING ACADEMY
Comands
• From Router B, what is the next hop to
– the 192.168.3.0 net?
– 10.2.0.2
10.3.0.2
10.3.0.1
10.2.0.2
10.2.0.1
10.1.0.2
10.1.0.1
192.168.4.0 Net
192.168.3.0 Net
192.168.1.0 Net
CISCO NETWORKING ACADEMY
B
Comands
• From Router B, what is the next hop to
– the 192.168.4.0 net?
– 10.2.0.2
– The next hop is always on the neighbor router!
10.3.0.2
10.3.0.1
10.2.0.2
10.2.0.1
10.1.0.2
10.1.0.1
192.168.4.0 Net
192.168.3.0 Net
192.168.1.0 Net
CISCO NETWORKING ACADEMY
B
Comands
• From Router B, what are the only two possible
next hop addreses?
– 10.1.0.1
– 10.2.0.2
10.3.0.2
10.3.0.1
10.2.0.2
10.2.0.1
10.1.0.2
10.1.0.1
192.168.4.0 Net
192.168.3.0 Net
192.168.1.0 Net
CISCO NETWORKING ACADEMY
B
Commands
• Static route - administrative distance parameter
• Optional
oak(config)#ip route 10.1.0.0 255.255.0.0 s0 121
oak(config)#^Z
Administrative Distance
CISCO NETWORKING ACADEMY
Commands
• Static route - administrative distance
• If unspecified, default distance is 0
for outgoing interface format.
• These routes will show as S but will be listed as
directly connected in the routing table.
oak(config)#ip route 10.1.0.0 255.255.0.0 s0
CISCO NETWORKING ACADEMY
Commands
• Static route - administrative distance
• If unspecified, default distance is 1
for next hop format.
• These routes will show as S (static) in the
routing table.
oak(config)#ip route 10.1.0.0 255.255.0.0 10.3.0.1
CISCO NETWORKING ACADEMY
Commands
• Configuring a default route (default network)
method 1 - set a default route to the wildcard
network & subnet of 0.0.0.0 0.0.0.0
Wildcard network & mask
hay(config)#ip route 0.0.0.0 0.0.0.0 192.168.0.1
hay(config)#^Z
See http://www.cisco.com/warp/public/105/default.html
CISCO NETWORKING ACADEMY
Route to default network via
this “next hop” address the address of the
direct neighbor interface.
Distributed from hayward to oakland by RIP
Commands
• method 1 - RIP will automatically redistribute the
default route to the wildcard network & subnet of
0.0.0.0 0.0.0.0 to other routers:
oakland#show ip route
Gateway of last resort is 10.2.0.1 to network 0.0.0.0
10.0.0.0/16 is subnetted, 2 subnets
C
10.2.0.0 is directly connected, Serial1
R
10.1.0.0 [120/1] via 10.2.0.1, 00:00:18, Serial1
R 192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:18, Serial1
S 192.168.2.0/24 [1/0] via 10.2.0.1
C 192.168.3.0/24 is directly connected, Ethernet0
R* 0.0.0.0/0 [1/0] via 10.2.0.1
CISCO NETWORKING ACADEMY
Commands
• Configuring a default route (default network)
method 2: (presented in the curriculum)
ip default-network xxx.xxx.xxx.xxx
Send default traffic here
hay(config)#ip default-network 192.168.0.0
hay(config)#^Z
See http://www.cisco.com/warp/public/105/default.html
CISCO NETWORKING ACADEMY
Commands
• Default network must be
– defined on each router
or
– redistributed by RIP to other routers
CISCO NETWORKING ACADEMY
Commands
• Redistribution methods:
– 0.0.0.0:
• With IOS Version 12.0, RIP automatically distributes a route
to 0.0.0.0 to other routers.
• With IOS Version 12.1 or later, you must add the
default-information originate command:
hay(config)#router rip
hay(config-router)#default-information originate
– ip default-network: To force RIP to redistribute the default route,
you must add the redistribute static command:
hay(config)#router rip
hay(config-router)#redistribute static
CISCO NETWORKING ACADEMY
Commands
• show ip route
• displays routing table
[Administrative Distance/Metric]
oakland#show ip route
Gateway of last resort is 10.2.0.1 to network 192.168.1.0
Route R
Source
C
C
R
R*
S
C
192.168.4.0/24 [120/1] via 10.3.0.2, 00:00:11, Serial0
10.0.0.0/16 is subnetted, 3 subnets
10.2.0.0 is directly connected, Serial1
10.3.0.0 is directly connected, Serial0
10.1.0.0 [120/1] via 10.2.0.1, 00:00:18, Serial1
192.168.1.0/24 [120/2] via 10.2.0.1, 00:00:18, Serial1
192.168.2.0/24 [1/0] via 10.2.0.1
192.168.3.0/24 is directly connected, Ethernet0
CISCO NETWORKING ACADEMY
Commands
• show ip protocols
oak(config)#show ip protocols
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 2 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Routing for Networks:
10.0.0.0
192.168.4.0
Update Distance: (default is 120)
CISCO NETWORKING ACADEMY
Commands
• show ip interfaces
• interface detail
oak(config)#show ip interfaces
Ethernet0 is up, line protocol is up
Internet address is 192.195.78.24, subnetmask 255.255.255.240
Broadcast address is 255.255.255.255
Address determined by non-volatile memory
MTU is 1500 bytes
Helper address is not set
Secondary address 131.192.115.2, subnet mask 255.255.255.0
Directed broadcast forwarding is enabled
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Split horizon is enabled
CISCO NETWORKING ACADEMY
Commands
• debug ip rip
• Displays rip updates as they are received & sent
by router
• Temporary troubleshooting only must not be left on!
• Turn off with
• no debug ip rip or no debug all
CISCO NETWORKING ACADEMY