سؤال عن Loopback Interface في الراوتر

[abu_Shihab]

ممكن حد من الشباب يشرح لنا الLoop Back Interface في الراوتر إلي فهمته انه يستخدم كrouter ID في الospf وانه يستخدم لعمل Troubleshooting ممكن حد يشرح لنا بالتفصيل وإذا ممكن حد يعطينا مرجع مناسب يتناول هذا الموضوع

شكرا جزيلا

[sheno]

اخى العزيز

as u said the loopback is used for determine the designated router in the ospf routing process

as u know the designated router is the router which has the hieghest ip or its the router which has a higher loopback
ip.

cisco advice u if u need to make an election for the designated router to implement a loopback interface to the router and assign it an ip

but why we use the loopback interface rather than the physical interface in the election process for the designated router
the answer is so easy
because the physical interface may be shutdown and become inactive for any disaster reason
but
the loopback is always active because its logical interface
so as the rourter is on as the loopback is on too .

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we can also use the loopback interfcae for implement
an access server router where we can control many routers by using a server router to control or configure all of them
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we can use the loopback also as atest for connectivity in wan routing and in ethernet interface also

whether in ( isdn - atm - framrealy - so on)

and there many methods to applay that kind of test
any way there is many article by cisco in how to use the loop back kinds




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:comp21: to be honest with you i am still discover every day
alot of benefits by this loopback interfcae. its
the magic key for alot of usage whether in cisco
or microsoft .

best wishes

[abu_Shihab]

السلام عليكم
i understand that so what you mean to say is when you make router ID as physical interface when that interface is down this means the second router with highest router ID will be elected as the DR correct so the loop back interface has nothing to do with the routing process or doesn't effect
any thing in the router functionality

[sheno]

look dear
if u let the election depend on the loopback interface which u already assigned so if any physical interface down this will not effect on the elction process why?
because the router is still power on its not means that any interface got down so the whole router go down too offcourse not because the router has another physical interface and more than this the router has its loopback interfcae which is logical interfcae and it will use in the election process between the routers to share in the election process
but if u dont assigne a loopback interfcae to the router and the router physical interfcae is got down offcourse without any doubt the elcetion will be influenced and then the routers will search for another designated router or offcourse the backup designated router will do its job
best wishes

[fastory]

يوجد بالرواتر نوعين رئيسيين من interfaces :
- physical interface مثل fastethernet interface و serial interface وهي منافذ محسوسة تشاهد بالعين
- virtual interfcae ولها نفس خصائص physical interface اي تأخذ ip address و description .... الخ لكنها وهمية لا تشاهد بالعين، وهذه النافذ تسمى loopback intefac

وهي موجودة لعدة استخدامات، فمثلا لو اردنا انشاء شبكة LAN من اجل الفحص والتجريب، فإنه يلزم احضار جهاز سويتش ووصله من خلال كيبل على منفذ Fastethernet عالراوتر إن وجد. لكن يمكن القيام بهذه العملية بكل بساطة من خلال loopback inteface بمجرد اعطاؤه ip address.

[abu_Shihab]

tamam

so if what ip address we should assign to the loopback interface

can we put any ip address or it should belong to one of the interfaces network ids

[sheno]

tamam

so if what ip address we should assign to the loopback interface

can we put any ip address or it should belong to one of the interfaces network ids

offcourse u can put any ip
but this ip u have to put in your mind that this ip must belong to adiffernet subnet than the other physical interface subnet
look u have to treat the logical interface ( loopback interface) as a physical interfcae .