Lessons Learned:
Redistribution from the RIP process into the OSPF process
When the RIP router originates routes as long as the OSPF
area is a normal area these are going to be TYPE 5 LSAs in the OSPF database. Either the E1 or E2 routes, By default the
routes will show as E2 and the default metric is 20.
Under the OSPF process –
We simply say –
R4(config-router)#redistribute rip
% Only classful networks will be redistributed (this is a backwards
compatibility feature – only clasful summarize will be included in the OSPF
database)
R4(config-router)#
This will advertise the RIP routes with the default values. To remove the classful subnets we need to add
the keyword “subnets to the redist – process.
R4(config-router)#redistribute rip subnets
This should advertise anything running RIP including the
connected interfaces running RIP into the OSPF database- TYPE 5 LSA”s
Type-5
AS External Link States
Link ID ADV
Router Age Seq# Checksum Tag
192.168.47.0
192.168.47.4 192 0x80000001 0x00C0AA 0
Or we can view the
External
LS age: 231
Options: (No
TOS-capability, DC)
LS Type: AS External
Link
Link State ID:
192.168.47.0 (External Network Number )
Advertising Router:
192.168.47.4
LS Seq Number:
80000001
Checksum: 0xC0AA
Length: 36
Network Mask: /24
Metric Type: 2
(Larger than any link state path)
TOS: 0
Metric: 20
Forward
Address: 0.0.0.0
External Route
Tag: 0
All other OSPF routers in the topology should show the RIP
routes as E2 routes:
R3#sh ip route
O E2 192.168.47.0/24
[110/20] via 10.1.43.4, 00:04:24, FastEthernet0/0
Also if we show the RIP route specifically
R3#sh ip route 192.168.47.0
Routing entry for 192.168.47.0/24
Known via "ospf
1", distance 110, metric 20, type extern 2, forward metric 1
Last update from
10.1.43.4 on FastEthernet0/0, 00:06:14 ago
Routing Descriptor
Blocks:
* 10.1.43.4, from
192.168.47.4, 00:06:14 ago, via FastEthernet0/0
Route metric is
20, traffic share count is 1
This says – the metric is 20 the type is 2 and the forward
is 1 – the forward is to get to the ASBR.
This is a function of the E2 routes. They separate the seed
metric plus the metric to the ASBR.
Note: the farther away from the ASBR the Forward metric will
increment. If there is ever a tie in the E2 routes, we will look at the forward
Metric for the best path.
Note: if we set these routes as External type 1 routes, then
there’s no difference between the metric and the forward metric. The only time
this really matter is when there are multiple exit points for the domain.
We can set the metric type during redistribution.
Verify –
We need to verify can we reach the destination from the other
protocol.
R3#ping 192.168.47.7
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.47.7, timeout is 2
seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max =
16/32/44 ms
R3#
And I can reach my RIP router. If we can reach the destination
we can assume the redistribution is correct. If the Routing domain is large
there would be a lot of checks.
For Verification of a large domain we can use TCL scripts
TCL – stands for the Tool Command Language – this is an open
standards language.
IOS – supports TCL 8.3.4
-99% of programming is outside the CCIS scope
-useful in redistribution for automating PING scripts
Only problem with TCL Scripts is the syntax has to be exact
and there’s not a real reference guide
TCL PING Script Example:
R3#tclsh (staring a
TCL Shell)
R3(tcl)#foreach X {
(this says create a forloop and define a variable X, for each value that
X has, run the ping command for the variables value. )
Ex:
tclsh
#foreach x {
+>(tcl)# 10.1.43.4
+>(tcl)# 192.168.47.7
+>(tcl)# 172.16.41.1
+>(tcl)# 10.1.16.6
+>(tcl)#} { ping $X }
The end result is it will ping these IP’s in order.
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