Async interface with routing

Answered Question
Jun 5th, 2007
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Hi, when configuring an async port with the following two commands:


async dynamic routing

routing dynamic


This allows the router to send and receive routing updates, correct? However, the config I am looking at also has the dialer interface which the aysnc interface uses set with the passive-interface command which should block that interface from participating in EIGRP.


So what I am wondering is if the dialer interface is in passive-interface mode then how come the async port can still send and receive routes? And if it can still send and receive routes, then how come the "show ip eigrp neighbors" command shows no neighbors?

Correct Answer by Richard Burts about 9 years 11 months ago

Will


Yes, I am saying that if the commands are enabled and the interface CAN send updates, that it will not send any updates until the routing protocol WILL generate updates. And when the interface is made passive that the EIGRP process will NOT generate any updates for that interface.


Another way of saying it is that the interface will send any updates that the routing protocol chooses to generate, but that the interface will not make up any updates on its own. Until the interface has updates generated by the routing protocol it will not transmit updates even though it CAN transmit updates.


HTH


Rick

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Richard Burts Wed, 06/06/2007 - 06:09
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Will


Perhaps there is something in your question that I have not yet understood completely. But it seems to me to be fairly straightforward. The 2 commands mean that the interface is capable of sending and receiving routing updates IF the router sends them. When the interface is made passive in EIGRP then the router will not send EIGRP updates. The interface is able to send but the routing process will not generate the update to be sent. That is why show ip eigrp neighbors command shows no neighbors - because the EIGRP process is not sending through the interface.


HTH


Rick

voiper_99 Wed, 06/06/2007 - 15:21
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Thanks for the reply Rick. What I am finding hard to understand is, as you and I said:


"When the interface is made passive in EIGRP then the router will not send EIGRP updates."


So if the router/aysnc port is not sending & receiving EIGRP updates, then what updates is it sending and receiving? Because at present EIGRP is the only routing protocol set up on the router.


EDIT: I just re read your post. In regards to your comment here:


"The interface is able to send but the routing process will not generate the update to be sent."


So are you saying that no routing is done even though those two commands are enabled?

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Richard Burts Wed, 06/06/2007 - 18:20
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Will


Yes, I am saying that if the commands are enabled and the interface CAN send updates, that it will not send any updates until the routing protocol WILL generate updates. And when the interface is made passive that the EIGRP process will NOT generate any updates for that interface.


Another way of saying it is that the interface will send any updates that the routing protocol chooses to generate, but that the interface will not make up any updates on its own. Until the interface has updates generated by the routing protocol it will not transmit updates even though it CAN transmit updates.


HTH


Rick

voiper_99 Wed, 06/06/2007 - 19:07
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ahh I see, thank you for clearing that up Rick.


I just have one more question for further clarification. The async port itself is not set as a passive interface, however, it is cloned from a dialer interface which IS set as a passive interface, seeing as though the async port is cloned from the dialer, that would mean the async port would "inherit" the passive-interface limitation, wouldn't it?

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