Some new imagefeature

1. Stub
Prevent the router from sending unnecessary queries. When a router is set to stub, other routers will not send queries to it.
You can set the advertised routes (connected, redistributed, static, summary, or receive-only)

2. Stub leaking
--- + ---------------- + ----

R1 r2

|
E0/0 |
R3---------------R4
E0/1 |
--- + ----
192.168.1.0
R1, r2 declares the default route to R3 and R4. R3 and R4 belong to a remote site and are set to stub. when the link between the R2-R4 down, since R3, R4 are stub, so do not send query, then R4 will not declare 192.168.1.0 to R3, R3 will not declare the default route to R4. at this time, the network 192.168.1.0 is completely inaccessible.
when R3 and R4 are stub, R3 can leak a default route to R4 and R4 will leak 192.168.1.0 to R1.
Configure the following command on R3
access-List 1 permit 192.168.1.0 0.0.255
access-List 2 permi T 0.0.0.0 0.0.0.0
!
route-map leaking permit 10
Match ip address 1
match interface E0/0
route-map leaking permit 20
Match ip address 2
match interface E0/1
!
router VPN 100
the IPsec connection protocol used by the VPN gateway to intercept 192.168.1.0 must be exposed to R3 on the Interface of R4 to R3. in this way, the above problem is solved.

3. Summary leaking
10.1.10.0/24 10.1.20.0/24... 10.1.250.0/24
----------------------------------------------------------------------
/\
/\
/\
10.1.1.0/24 | ----- R1-----------R2 ----- | 10.1.2.0/24
\/
E0/0 \/E0/0
\/
\/
R3
For R1, R2 is required to send 10.1.0.0/16 to R3 and select the optimal path for R3 to reach 10.1.1.0/24 and 10.1.2.0/24, r1 and R2 also need to declare the 10.1.1.0/24 and 10.1.2.0/24 that are directly connected to them to R3. in this case, the previous approach is:
R1:
Interface E0/0
IP Summary-address subnet 100 10.1.0.0 255.255.0.0
IP Summary-address egirp 100 10.1.1.0 255.255.255.0
After using summary leaking:
R1:
Access-List 1 permit 10.1.1.0 0.0.255
!
Route-map leaking permit 10
Match ip address 1
!
Interface E0/0
IP Summary-address VPN 100 10.1.0.0 255.255.0.0 leak-map leaking

4. Summary only
10.1.10.0/24 10.1.20.0/24... 10.1.250.0/24
----------------------------------------------------------------------

R4
/\
/\
/\
/\
R1-----------R2
\/
E0/0 \/E0/0
\/
\/
R3
Require R1, R2 to aggregate its upper network as 10.1.0.0/16 to R3, and for security reasons, do not want R3 to know the link 192.168.x.x between the R1-R4 and the R2-R4, the original practice:
R1 summary on E0/0 and configure distribute-list. Only 10.1.0.0/16 can be sent to R3.
Now you can do this:
R1:
Interface E0/0
IP Summary-address subnet 100 10.1.0.0 255.255.0.0
IP Summary-only glas100

5. Stub co-existence
Hub Router

--------------------------------------

R1 R2 r3
In the multi-access network, if R1 is a stub router, then R2 and R3 must also be stub router; otherwise, the hub router still sends a query request.
Some people manually specified neighor to avoid this problem, but the scalability is very poor. After manually specified neighbor, only unicast can be used and the multicast package will be rejected. therefore, to add a stub router in the multi-access network, add a neighbor command to the Hub router.
After improvement:
* Hob router uses the multicast package
* Spoke router can accept the multicast packet even if you manually configure neighbor. In this way, part of the spoke router in the multi-access network can use unicast, while some spoke router use multicast.
* In the multi-access network, the hub Router does not send a query to the stub router. For the non-stub router, the hub router sends a query
* In the multi-access network, if unicast is used to send a query to the non-stub router and the number of non-stub router exceeds 5 or 10% of the total number, the efficiency will be very low, when encountering so many non-stub router, we recommend using multicast to issue a query.

6. iegrp supports Graceful Restart. As a summary, distribute-LIST Command, Graceful Restart is performed instead of re-establishing the neighbor relationship. if peer resynchroniazation is not supported, NSF-Restart is performed.