Questions tagged [ipv6]

For questions about Internet Protocol version 6 (IPv6); as specified in RFC 8200.

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Many SYN_RECV connections in netstat [closed]

When I do netstat -tn, I consistently see a lot of connections from a few ipv6 addresses (the fe80:: ones; usually around or exactly 4096 of them). I'm unable to find the addresses on WHOIS, and ...
5 votes
2 answers
578 views

Can a jumbogram (giant data packet) be used at a large scale (in WAN for example)?

There are many scientific paper for Jumbo frame, even more, some real implementations and deployments. But it is not the case for Jumbogram !! Jumbo frame (geant frame) for Layer 2; Jumbogram (geant ...
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15 votes
5 answers
4k views

Why do we need ports with IPv6?

My understanding is there are 2^32 - 1 possible IPv4 addresses, and 2^16 - 1 possible ports. Which gives ~2^48 addresses. The additional 2^16 additional ports seem almost insignificant considering the ...
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1 answer
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IPv6-over-IEEE802.15.4 Multicast scope

An IPv6 Multicast address is defined as | 8 | 4 | 4 | 112 bits | +--------+----+----+-------------------------------------+ |11111111|flgs|scop| group ID ...
1 vote
2 answers
95 views

IPv6 subnets without delegated prefix

I have received an IPv6 network from my provider, say it's 2001:db8:1::/48. I did not get delegated prefix from them. I would like to use the IPv6 addresses on different networks behind a firewall (...
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What is the maximum safe UDP payload size over IPv6? [duplicate]

I am developing a networking library (that uses exclusively UDP) and I want to support both IPv4 and IPv6 by using a dual-mode socket. I want to limit the size of the packet user can send to a value ...
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3 votes
1 answer
229 views

Does Network Discovery (rfc2461) preclude ARP sniffing?

I'm debugging a system demonstrating intermittent loss of connection. It's loosing entries from the neighborhood cache while there are active connections. Does Neighbor Discovery (rfc2461) require ...
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How many /56's are there in a /49 IPv6 [duplicate]

I am studying subnetting in IPv6. I came across the following question from a website called Subnetting Practice, which I will quote below. How many /56s are there in a /49? Could someone please ...
0 votes
2 answers
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Simple IPv6 Global Unicast question

I was reading this article which states: RFC 3587 states that out of the 128 bits in IPv6 addresses, left most three bits are must be fixed as 001. Remaining 45 bits are reserved for global routing ...
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2 answers
73 views

Will there be an easy way to identify local Ipv6 addresses like with Ipv4?

When using WireShark, WNetWatcher, or any packet analysis tool, it's very easy "at a glance" to identify packets that are originating from the local network versus the Internet, since their ...
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1 vote
1 answer
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Understand DSCP and Precedence Values in Ipv4 or Ipv6 packet

I read from this website to understand DSCP and it's corresponding IP precedence value. For example DSCP value is '000 000' which Drop Probability is N/A(never happen) and it's Equivalent IP ...
0 votes
1 answer
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Does socket address include transport protocol (http://)? [closed]

Let's say I have the following: http://ip_addr:port This is supposedly called the socket address (see sources below), but I can't find a conclusive answer anywhere if the transport protocol (http://) ...
1 vote
0 answers
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How do I set up IPv6 multicast over an MPLS carrier?

I'm setting up an MPLS carrier with VPNs in GNS3, using Cisco 7200 routers. Exact version I'm using is C7200-ADVIPSERVICESK9-M Version 15.2(4)S5, but I'm willing to upgrade/change if that's needed. On ...
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2 votes
1 answer
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Which ranges of IPv6 and IPv4 do requests to the local network and the host?

I'm looking for the range of IP address that is bound to the local network or the host itself. So far for IPv4 I found: 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255....
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IPv6 Subnetworks Explanation

Can somebody help me get a better understanding of IPv6? For me, v4 is considerably easier to wrap your head around. Some questions I still have after a few hours of reading: Maybe the simplest one: ...
1 vote
1 answer
35 views

What "IVI" from "IVI Translation" stands for?

In several documents in the context of IPv4/IPv6 transition I see these three letters "IVI" that seems to be an acronym, but I was unable to find what it means or suppose to refer. Maybe is ...
1 vote
1 answer
70 views

Is an ICMPv6 neighbor advertisement meaningful if no options are set?

This is what I think a normal ICMPv6 neighbor advertisement should look like: It says "I'm 2001:57a:d000::54 and you can reach me at 02:02:53:85:21:25". This is what neighbor advertisements ...
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0 votes
2 answers
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How does all 54bits after FE80/10 should be set to 0 apply?

I read on a website: " link local addresses use the address block of Fe80::/10 (from FE80:: to FE80:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF). However, the standard states that the 54 bits after FE80/...
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6 votes
1 answer
668 views

IPv6 prefix interpretation

I have a very basic question about IPv6 prefix. Taking a very simple example about prefix notation: "2001:db8:abcd:0012::0/64" My question is: Do we call the whole thing under quote as ...
3 votes
1 answer
188 views

IPv6 neighbour discovery blocked by MLD snooping switch

I recently noticed that my IPv6 multicast traffic was being broadcasted to all hosts connected to a switch, even those that had not subscribed to the traffic. To fix this, I enabled MLD snooping on ...
1 vote
1 answer
58 views

OSPFv3 Authentication IPSEC SPI/Logging issues - Can you filter out logs?

I'm running into a problem with our Cisco ASR-1002HX and ASR-1006X. I have a mix of Juniper and Cisco routers all configured exclusively with IPv6. All of our routers are in the same ospfv3 area 0. We ...
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2 votes
2 answers
157 views

IPv6 link-local address

Can somebody explain why we can assign link-local address FE80::1 to both interfaces? What does it give to me ? R1(config)# interface g0/0 R1(config-if)# ipv6 address fe80::1 link-local R1(config-if)# ...
0 votes
1 answer
197 views

Is it possible to do SLAAC with Route Advertisement *without* default-route? [closed]

I have a router with IPv6-ULA networks. It's running Linux with Systemd-networkd if that matters. Now I'd like to auto-configure clients in one network so that they will have an address in one of the ...
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1 vote
1 answer
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Why solicited-node multicast address while all-node multicast address can do the same thing?

Why bother plugging in the last 24 bits of the sender's unicast address into the solicited-node multicast address while all-node multicast address can achieve the same thing? In my view, this move is ...
2 votes
2 answers
72 views

Does it require a DAD when generating link-local address in IPv6

In IPv4, link-local addresses are checked to be unique using an ARP request. But in IPv6, as it is generated by a EUI-64 or hash. It is assumed to be unique (I suppose). But does it require a DAD (...
0 votes
1 answer
61 views

What is the reason behind not returning unused IP addresses? [closed]

There are several companies out there with one or more /8 IP addresses, for example: DoD has more than 200 million, HP has one /8 (>16 million), Apple has one /8, General Electric has one /8, IBM ...
1 vote
2 answers
170 views

Calculating Checksum for ICMPv6 Packet

I have a packet that has a checksum of 0xffff, and a calculated checksum of 0x0000. I know in UDP, a checksum of 0x0000 is not allowed, and is instead replaced with 0xffff, thus the packet should be ...
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1 vote
5 answers
342 views

If IPv6 exists, why do we still pay for static IPv4 addresses?

Given that there is some ridiculous number of IPv6 addresses per every single person on the planet, why do ISPs still charge for IPv4 addresses? Why not just give the user an IPv6 address? Is it ...
2 votes
1 answer
1k views

Which one is right, UDP has 508 or 512 bytes payload limits?

We know the size guarantees the datagram won't be fragmented in IPv4 is maximum 576 bytes. But the size when use UDP header 8 bytes and if we take UDP payload 512 bytes and choose maximum header size ...
0 votes
1 answer
48 views

Do IPv6 addresses have better persistence with DHCPv6?

I have a LAN with about 25 devices that occasionally grab each other's IP address via DHCPv4. I know there are certain lease time limits and it can be set to very long periods to work it around to an ...
1 vote
1 answer
112 views

Are IPv4 type of service and IPv6 traffic class equivalent to each other or is traffic class IPv6 specific? [duplicate]

IPv6 has a traffic class field. According to the specification it is an IPv6 length, out of which first 6 bits are called code point or differential services code point (DSCP) and the last 2 bits are ...
0 votes
2 answers
360 views

Is it possible for TCP can accept out of order segments?

TCP is connection-oriented protocol whereas IP isn't connection-oriented protocol. Any packets before sending into transport layer sorted operation must have been done in network layer. That's why we ...
3 votes
2 answers
304 views

Why can IPv4 and IPv6 use strict source routing(in options field) and flow label respectively inspite of connectionless protocol?

In IPv4 option field one field option is source routing option this means packet will always be routed by router Or not. Packet can also be routed by source such routing is known as source routing. ...
1 vote
1 answer
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How to configure IPV6 /53 subnet on packet tracer?

I have tried configuring a Ipv6 subnet address 2001:0dce:0000:0000::1/53 into the router interface. It works but when the I tried setting the auto-configuration button on the PC connected to this ...
1 vote
4 answers
244 views

IPv6 addresses plan and allocation

I read at several places that ISPs should allocate a /48 (or /56) IPv6 addresses blocks to end users Wikipedia for instance The RIRs assign smaller blocks to local Internet registries that ...
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4 votes
1 answer
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Traffic sent to GRE Tunnel fails, but GRE Tunnel is up and OSPF adjacencies are formed

NEW INFO_7-12-21 R1#sho ipv6 rout 2001:db8:B2:200::2:2 Routing entry for 2001:db8:B2:200::2:2/128 Known via "static", distance 1, metric 0 Route count is 1/1, share count 0 Routing ...
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2 votes
1 answer
570 views

Static IPv6 Route on Ubiquiti EdgeRouter for my own /64

I am colocating some hardware in a local datacenter, and I'm trying to get IPv6 going. My datacenter has assigned me a /64, but they have given me a gateway address within that /64. The gateway (that ...
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2 votes
1 answer
72 views

EUI-64 on a loopback address

A loopback address does not have a MAC address. How then does a loopback interface get assigned an EUI-64 address? I ran an example on packet tracer, and the loopback interface successfully acquired a ...
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1 vote
0 answers
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Why cant my network send packages but piv6 pings go through?

I have the following network: My routing is as follows: Device configuration for ISP: Building configuration... Current configuration : 1388 bytes ! version 15.1 no service timestamps log datetime ...
0 votes
2 answers
58 views

How to create a mapping between TCP segments or IP packets or fragments and TCP Windows? [closed]

I am searching for a method how I practically can determine the segments within a TCP window both when sending and receiving them? I want to modify IP packets per TCP window. I already looked into the ...
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2 votes
2 answers
136 views

Unable to add an abbreviated IPv6 to a Cisco router

I am very new to networking and playing around with GNS3. I am trying to configure a router to have 2 IPv6 addresses in a single interface (as far as I understood, this is possible with IPv6) I ...
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-1 votes
1 answer
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why is the adress prefix for global unicast adresses in ipv6 considered 3 bits?

global unicast adresses in ipv6 always start with number 2 or 3, but 2 or 3 takes only 2 bits , and the whole adress is represented in hexadec which takes 4 bits not 3, so why the prefix is 3 bits ?
2 votes
1 answer
733 views

I can't ping the gateway IP (fe80::1) from the internal port in my fortigate 60f firewall

I am using a fortigate 60f firewall. I have configured it for both ipv4 and ipv6. I have used the SD wan (by adding wan1 and wan2) for load-balancing. Moreover, I have configure a default static route ...
1 vote
1 answer
142 views

How does a device receive default gateway IP address?

When and how does a device get information about default gateway in LAN? I know you can define default gateway statically, but which protocol is used when it is not statically defined? Is it from ...
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1 vote
1 answer
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Can servers derive the user IPv6 block of an address?

Internet Service Providers (ISPs) assign users large IPv6 blocks (~/64) containing millions of IPv6 addresses. If a user was to ping a server using 2 different IPv6 addresses from his given IPv6 block,...
0 votes
1 answer
71 views

Why does a Cisco router advertise a prefix with NDP RA when it has an address in that range?

If I write interface Vlan1 ... {ipv4 config} ... ipv6 address 2001:DB8:5432:101::/64 eui-64 ipv6 address FDAA:DB8:5432:101::/64 eui-64 ipv6 enable ipv6 nd prefix 2001:DB8:5432:101::/64 ipv6 nd ...
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2 votes
0 answers
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Can I route DHCPv6 & Router-Advertisements through another router? [closed]

I have asked this question on Super-User, though I'm not sure, it's the best place. 1 I believe this Exchange is a more appropriate place to ask: I have a dual router setup (two routers behind each ...
3 votes
1 answer
95 views

Recommended IPv6 prefix size for PPP to a single host?

I am using PPP to create a IPv6 connection to a remote host. What is the recommended IPv6 prefix size for a single host at the other end of the PPP connection? Should it be /128, because there is ...
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5 votes
2 answers
1k views

Can a client-side outbound TCP port be reused concurrently for multiple destinations?

Can a client-side outbound TCP port be reused concurrently for multiple destinations? If it's possible, this would let NAT gateways milk an IP Address much more, and make it practically impossible to ...
4 votes
2 answers
267 views

IPv6 Prefix Delegation & propagation through an organisation

IPv6 Prefix delegation is designed to allow an ISP to give an organisation a block of addresses to issue throughout their network. However, enterprise networks extend beyond a single tier of devices, ...

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