31

classful addressing is "a thing of the past". This is true because nothing in the modern internet does classful addressing[1]. With classful addressing, the netmask is a fixed value based on the address. In your example, you cannot "merge" three class C ranges to have 700 hosts in one LAN. The netmask for each range is automatically 24 bits. CIDR fixed ...


23

Address delegation really used to happen in three sizes: class A, B and C. Class A delegations would be given from a certain address range, class B delegations from a different range etc. Because the different classes used different address ranges you could determine the class by looking at the first part of an address. And this was built into the routing ...


16

Classful addressing only supports 3 masks for unicast: /8, /16/, /24. CIDR allows the mask to be any value from /0 to /32. Think of a point-to-point serial: that would have wasted a class C /24 (256 xIPs) with a classful setup before; with CIDR it only needs /30 (4 xIPs) or /31 (2 xIPs). Most ISPs will now only assign a /28 to a customer providing 14 IPs, ...


9

Since the summarized route means that a router advertising it has knowledge of the individual routes within the summarized prefix, it is more trustworthy than the same (summarized) prefix being advertised as an individual route without the knowledge of the individual routes which make up the summary. This doesn't mean that the summarized route is more ...


8

TLA/NLA structure for IPv6 addresses The TLA/NLA allocation structure has been deprecated in RFC 3587, August 2003: 2. TLA/NLA Made Historic The TLA/NLA scheme has been replaced by a coordinated allocation policy defined by the Regional Internet Registries (RIRs) [IPV6RIR]. Part of the motivation for obsoleting the TLA/NLA structure is ...


8

This will work but it would be a poor design choice (IMHO) unless you have a specific reason for doing so. See this discussion: Duplicate OSPF area IDs OSPF Best Practicies Recommended OSPF configuration best-practices (using the SSM example) OSPF area configuration best practices Update #1: For the sake of completeness, I mocked up this situation using ...


7

This appears to be a Cisco router. Cisco has the aggregate-address command. You can advertise the aggregate address and all the individual addresses: aggregate-address 8.0.0.0 255.0.0.0 or only the aggregate address: aggregate-address 8.0.0.0 255.0.0.0 summary-only As long as even one prefix in the aggregate is in the routing table, the aggregate will ...


7

Regarding the question of splitting area 1 across the backbone (area 0): [area 1, subnet 1]---[ABR #1]---[area 0, subnet 2]---[ABR #2]---[area 1, subnet 3] [area 1, subnet 1]---[Router #1]---[area 0, subnet 2, end device #1]---[Router #2]---[area 0, subnet 2, end device #2]---[Router #3]---[area 1, subnet 3] Short answer: There is no problem with your ...


6

The AD of the EIGRP summary route is 5 only on the router that has the summary route configured. When the summary is advertised to other routers it has an AD of 90. The reason for the low AD is to insure that the summary route (to nul0) is preferred to prevent routing loops.


6

As many answers already explain, classes are a thing of the past because they do not allow subnet masks other then /8, /16 and /24. These specific subnet masks are still very popular, especially /24, because they are the easiest on us humans. For these masks, the end of the subnet part of the address lines up with a dot in the (dotted-decimal) IP address. ...


6

Generally speaking, route summarization hides information about more specific routes. It also hides the fact that you may not have a route to all addresses in your summary. So yes, you can summarize. Whether or not you should depends on what you are doing with your summary. In the case of BGP, you are advertising that you can reach all networks in your ...


3

I think what the question is about is if BGP will install the summarized route, if that middle subnet does not existing in the IP Route table. If that's the case, then the answer is yes, it will as long as one of the routes is in the BGP table: show ip bgp | i 192.168.0. You'd want to look to see if the 192.168.0.0/28 or 192.168.0.32/28 routes exist there....


3

I made this example to try and demonstrate it for you: You only need the first and last addresses: 192.168.1.0 11000000.10101000.00000001.000000000 192.168.120.0 11000000.10101000.01111000.000000000 To summarize you look at how many bites are the same, in this case the first 17 bites are equal: 192.168.0.0 11000000.10101000.00000000.000000000 = /17 or ...


3

It's because they are in the 10.0.0.0 network, and they are subnetted as /24. You are not seeing a route summary. If you had subnetted one differently than the other, say /25, you would get something like: 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 10.1.1.0/25 is directly connected, FastEthernet0/0 C 10.1.2.0/24 is directly ...


2

RFC 2450 - Proposed TLA and NLA Assignment Rules Microsoft's is in line with the proposed IETF RFC 2450. Since it's still proposed, it isn't finalized, but it's the likely end format.


2

In Classful routing, the netmask is implied by the top bits of the address, and is not stored in routing tables; the class is a property of each address, not just of the routing topology. A Class C network cannot be a subset of a Class B network, because the top bits cannot match both. Your hypothetical organization with 3 Class C networks would have to ...


2

Danis, you have the right idea. To answer the question what is the diffrence ... FLSM can be thought of like address summarization that can't be taken apart. FLSM can be efficient at routing because it doesn't even need the whole IP to do its routing but it is an inefficient use of ip addresses since it reserves the whole block for 1 subnet only. The FLSM ...


1

The aggregate route is useful for reach-ability outside the area or AS where detailed routing information is available for the covered routes. Inside such an area, the reason aggregates default to reject is so unused addresses -- those which are un-routed -- can generate an ICMP unreachable reply. When someone tries to connect (for example, with TCP) they ...


1

The configuration you have shown is correct and will work as long as EIGRP is working over your serial link


1

I think this might help: https://networkdirection.net/EIGRP+Design Also check out the references on the page. Basically, summarization provides a natural boundary where queries are stopped.


1

LSA 3 summarizes the TOPOLOGY, not the routes. If you look at the ospf database within an area 0 router, there should be a type 3 LSA for each ROUTE/prefix within the other area(s). There is a key distinction between this vs knowing about the ROUTERS in a Type 1 LSA. Type 1 LSA = Router (NODE) in the OSPF GRAPH + links Type 3 LSA = ROUTE from other ...


1

It depends if you are seeking to find the single summary network that covers at least all of your list, or the shortest list of networks that covers your list exactly. In the first case, what Bungicasse described works. In the second case, it's not very difficult, and is a lot like the problem of handing back change for a payment with a minimal number of ...


1

Without the binary Where is the change happening ? - in the third octet How big a block size do i need ? - Well its 0 - 6 in the 3rd octet, so a block size of 6 would be great but there is no such thing, so 8 will do. (block-sizes 2,4,8,16,32,64,128,256 etc etc ) Right i now know that i need a block size of 8, how many bits do i need to borrow to ...


1

10.10.0000 0000.0000 0000 10.10.0000 0 are the common bits, the network bits 000.0000 0000 are the bit that are dedicated to host on your network 10.10.0.0/21


1

Yes. The number of bits in common is the number you are looking for. You left off the first 16 bits (they are in common). plus the 5 bits in common you show here is 21 bits in common.


1

The only place I've seen actual classful behaviour in recent years is in the point-to-point tunnelling protocol. PPTP Many would consider this to be obsolete in itself, but there is certainly a lot of it still in use. When the client connects to a server, the tunnel gets either a default route or a route to the classful network of the server. https://...


1

Well you normally need to use virtual links to talk to area 0 via a different non area 0 area or you connect 2 parts of area 0 through a non zero area. So virtual links do not apply. You can have a non contigious area if its not area 0, but as hinted above, not really a good idea. That being said you proposed topology will work without virtual links.


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