Routing Issue

[jain.manish94]

Hello Mark, 

where we apply Stub in OSPF . actually i was doing a practical in GNS and applied Stub in ABR so  my Virtual link was not working . can we apply virtual link or not . in this case what should i do.

[Mark Malone]

That's a design issue you cant use stub when your using virtual link

stubs can go on abr to reduce the size of the lsdb but not when using virtual links , virtual links wont work through transit stub areas

The only way of my head to get around that is use gre tunnel there probably is other methods as well

[jain.manish94]

Where we apply passive interface in OSPF and EIGRP. 

[Mark Malone]

Its best practice to apply it as default in both processes and then open up what interfaces you want to learn information from

[jain.manish94]

ok  , what where we apply it. i mean in Lan environment , wan environment or any other i am getting some confusion, because if i apply it will not send and receive any hello or information from neighbour 

Then what is the benefits of it...

[Mark Malone]

Its used for security most of the time tp prevent attacks and unwanted connections , you could also be connected to a 3rd party company within your network you may not want to advertise your networks to them

http://searchnetworking.techtarget.com/tip/Using-passive-interface-to-prevent-DoS

[jain.manish94]

but here if i need to ping in 3rd party company but i have applied passive interface in that case what i will do. 

[Mark Malone]

use a distribute list like the doc to control updates

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13675-16.html

[Richard Burts]

While security is one frequent reason to use passive interface it is certainly not the only reason. Let me suggest two other situations in which you might choose to use passive interface.

1) Think about a router or layer 3 switch that has two LAN interfaces and a WAN interface. You want to advertise the LAN subnets over the WAN so you enable the routing protocol on all 3 interfaces. But you know that there is not another router connected on either of the LAN interfaces. So why send hello messages and routing updates on the LAN interfaces. To conserve bandwidth use you might want to make both LAN interfaces passive.

2) Think about 2 layer 3 switches that are connected to each other. What if there are 10 vlans configured and each switch has an SVI in each VLAN. If you enable the routing protocol on each interface then switch A will send 10 sets of hello messages and 10 sets of routing updates to switch B. And switch B will send 10 sets of hello messages and 10 sets of routing updates to switch A. You might want to have a couple of vlans sending routing hello and updates to provide redundancy. But you would probably want most of the vlans to be passive interface for the routing protocol.

HTH

Rick

[Joseph W. Doherty]

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Posting

I just wanted to emphasis Rick's point 2, that not having some redundant path links, configured at transits, can also save on things like OSPF's shortest path computations (although the newer Cisco implementations that support ISPF might minimize such impact).

[jain.manish94]

Hello Team, 

i have 6 router in series connected to each other how to set communicate please tell me . 

Like .

R1--R2--R3--R4--R5---R6

Please check my attached file and tell me how many ABR here and How Many VL we can make to establish communion 

Please check both diagram. 

[jain.manish94]

But Richard, According to your point 1. 

Now how Lan PC will communicate with Wan , Suppose want to run internet on Lan PC . how is it possible now after applying passive-interface on Lan Port.

[Richard Burts]

Your question seems to be based on the assumption that when you make an interface passive that it makes the interface stop functioning. That is not the case. When you make the interface passive it just stops sending and receiving routing updates on that interface. It has no effect on the ability of the interface to send and receive data packets. So in my point 1 the router or layer 3 switch is sending and receiving routing updates on the WAN but not on the LAN. So a PC on the LAN is configured with a default gateway which points to the router or layer 3 switch. When the PC wants to access the Internet it sends the packet to its default gateway. The router or layer 3 switch receive the packet and use its routing table to forward the packet to the Internet. The fact that the LAN interface is not sending or receiving routing updates has no impact on the PC traffic.

HTH

Rick

[jain.manish94]

i just got one problem here.

CPU utilization for five seconds: 100%/5%; one minute: 99%; five minutes: 99%

uSecs   5Sec   1Min   5Min TTY Process

 494     4168224    242995      17153 88.43% 89.09% 89.13%   0 MLD_SNOOP

what does this means

[jain.manish94]

yesterday i connect two router . 

R1 to R2. 

on R1 interface gi1/0 i set --- ip ospf hello interval 1 -- ip ospf dead-interval 2

on R1 interface s1/0 left as it.

on R2 same on gi1/0 and same on s1/0 . 

i created one loopback on R1 -- int lo1 --- 10.10.10.1 

pinging from R2 --- ping 10.10.10.1 re 1000

and shut on R1 -- int gi1/0 -- shut 

but here why it was showing RTO because i set 1 and 2 hello and dead interval respectively 

is there any problem in my gns or how to do this please reply ..