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20 votes

Where can I use the IPv6 documentation prefix

The IPv6 documentation prefix (2001:db8:::/32) must be used ONLY for documentation purposes. It means written examples, diagrams, PPT presentations, Textbook explanations, etc. This range shouldn't ...
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15 votes
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IPv6 prefix interpretation

From RFC4291 section 2.3: An IPv6 address prefix is represented by the notation: ipv6-address/prefix-length The whole thing is called prefix. First part up to / is called address. Second part ...
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11 votes
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Possible (bit) patterns of a netmask

RFC950 states that Since the bits that identify the subnet are specified by a bitmask, they need not be adjacent in the address. However, we recommend that the subnet bits be contiguous and located ...
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11 votes
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Where can I use the IPv6 documentation prefix

If your test environment is separated from your local network you hypothetically could use any IPv6 addresses which are not reserved for special uses. However, if you are looking for an equivalent of ...
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8 votes

Where can I use the IPv6 documentation prefix

Just from the RFC I can't see anything defining that documentation is strictly written text. Do you have any source for this interpretation? According to the IANA IPv6 Special-Purpose Address ...
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8 votes
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Does IPv6 Prefix Delegation work with SLAAC, without the need of a DHCPv6 server/client?

Prefix delegation is a DHCPv6 option. You cannot do it without DHCP. Here is the RFC: https://www.rfc-editor.org/rfc/rfc3633
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7 votes

What determines the private ip addresses?

Classful networking died in 1993 and was replaced by CIDR. With CIDR, any subnet prefix length is possible. You can use 192.168.0.0/16 just as well as 10.0.0.1/31 (for private addresses). Nobody stops ...
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7 votes

Which ranges of IPv4 addresses cannot be expressed in prefix notation?

The issue is that you end up comparing unequal things when you say "I would express the range as 121.34.56.64/24 in prefix notation" The range 121.34.56.64 to 121.34.56.128 is contained in 121.34.56....
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7 votes

Prefix list BGP 0.0.0.0/0 and 0.0.0.0/ le 32

ip prefix-list out seq 10 permit 0.0.0.0/0 will match only a default route (0.0.0.0/0) whereas ip prefix-list out seq 10 permit 0.0.0.0/0 le 32 will match anything thats within 0.0.0.0/0 with a prefix ...
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6 votes

Possible (bit) patterns of a netmask

If you are using prefixes and networks, then the answer is no, the bits need to be contiguous. There are cases where a wildcard mask (inverse of mask) can be used, e.g. Cisco ACLs, and those can be ...
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5 votes

How to convert size represented in one prefix length to another?

How can I convert that to a size in /30? This question does not actually make sense. How many /30 equals to one /64? Neither does this question make sense. I assume you mean IPv6 because there ...
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5 votes

What does it mean to lease an IPv4 block?

When you lease an ipv4 block what do you actually get? The right to use those addresses on the Internet. How do you get access to the ip adresses? Is any special equipment required or is it as ...
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5 votes
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Simple IPv6 Global Unicast question

Left most 001 are fixed, this means the left most nibble can be: 0010 = 0x2 0011 = 0x3 The 4th left most bit is not fixed.
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4 votes

Possible (bit) patterns of a netmask

No. A netmask is a continuous series of ones. (The others are "wildcard" patterns.)
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4 votes
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Shorter prefix vs smaller prefix

I would assume /17 to /32 are the smaller prefixes. Prefix is used as a synonym (1) for network in this case. The prefixes are longer, thus the networks they describe are smaller. I can see this ...
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  • 4,601
4 votes

Problem with longest prefix matching

So, according to longest prefix matching rule, we send this packet to net2. That is correct. Now I have a doubt that all the packets which match with both networks are sent only to net2, instead, ...
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4 votes
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Question about BGP peering with your ISP

There are generally two reasons to use BGP with your ISP: You have more than one connection to your ISP(s), and you want to influence which path your traffic takes. You have your own provider ...
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4 votes

Recommended IPv6 prefix size for PPP to a single host?

RFC 6164, Using 127-Bit IPv6 Prefixes on Inter-Router Links explains that /127 networks are good for point-to-point links: Abstract On inter-router point-to-point links, it is useful, for security ...
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3 votes
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Find which VRF contains a route

If you want to limit your output to just the names of the routing-tables, then something like: show route 192.169.0.0/24 | match dest will do the trick
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3 votes

What determines the private ip addresses?

What determines the class of private ip addresses? Nothing because network classes are dead (please let them rest in peace), killed in 1993 (over 25 years ago, before the Internet went commercial!) ...
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3 votes

Possible (bit) patterns of a netmask

When TCP/IP first came out and got widespread, there were actually a lot of subnets with non-contiguous masks. But as addresses became scarce, the overhead to the rest of the net to allow global ...
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  • 346
3 votes

How to choose IP address and subnet mask while forming a network

Network classes are long dead, obsoleted in 1993 by CIDR, before the Internet went commercial. You should dump any book on IP from before that year. Classful networking may be interesting for ...
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2 votes
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IPv4 and IPv6 gateway subnet differences

A gateway is the host on a network that knows how to reach other networks. Your host would need a gateway just to reach a gateway on a network to which it is not directly connected. An IPv6 host will ...
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2 votes

How to test an IP against a prefix list on JUNOS CLI

In Junos you have the command: test policy <<POLICY-NAME>> <<Prefix>> however, it doesn't do quite what you are asking. Firstly, create your prefix-list and match it in a ...
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2 votes

Can I add a hop by dividing my prefix?

What does stop you from bridging these two interfaces? Simple transparent bridge. In this case you save 1 IP address. For all internal devices the GW is the IP of the router. For external devices, ...
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2 votes
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Can I add a hop by dividing my prefix?

You can subnet the /27 into /30 for the WAN link. That will leave you with another /30, a /29, and a /28 for you to assign on your network. Like this: 90.10.200.32/30 for the WAN, use 90.10.200.33 ...
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2 votes

BGP - Active\Passive Setup, except one AS

Short answer: you can't. You are asking to route traffic not by the destination address, but by the source address. In other words, you want traffic to take a particular path based on its source ...
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1 vote
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Does segment routing protocol steer packets based on best (longest) prefix matching?

Subnet routing is usually by destination address (as opposed to policy-based routing where other parameters can be used). The routing algorithm selects the most specific, longest subnet prefix from ...
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