Questions tagged [ipv6]

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

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votes
1answer
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Rogue RA what is this and how to counter it?

This content comes from one of my lectures on "security" module related to IP V6 section. There is no reference in the suggested book or lecture slides what that exactly is. However it is constantly ...
5
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1answer
1k views

Strange IPv6 packet seen when enabling interface on Juniper MX

I have two MX80 routers which are connected. When I enable the interface on one router I get the following packet from the other router which I can't explain: 17:23:46.004429 In IP6 (hlim 1, next-...
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2answers
3k views

IPv6 RA SLAAC prefix lifetime

From what I understand, there is no way to change the prefix lifetime once hosts install the prefix. If I shorten the valid/preferred timer for a prefix, it has no effect on hosts already using the ...
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3answers
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ipv6 addressing /127 vs eui-64

Best practice is to use a manual /127 address for point to point addressing described here RFC2373 for EUI-64 ERFC 2373 dictates the conversion process, which has two steps. The first is to convert ...
9
votes
2answers
4k views

Configure External Interface for DHCPv6 client on Cisco IOS

What are the necessary steps to configure IOS 12.4(25f) to support IPv6? Comcast is the ISP, and I'll be using a Server 2012 box for internal DHCPv6. I'll need to grab a DHCPv6 address from Comcast ...
9
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1answer
1k views

Blocking IPv6 RA advertisements on Juniper EX series switch

How do I go about blocking IPv6 RA advertisements on access ports on a Juniper EX series switch? I know that Cisco offers ra-guard as an option much like bpdu-guard on spanning tree, I am just not ...
39
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5answers
7k views

Why does ipv6 specify 128 bit address, when there are only 48 bits in MAC addresses?

So, I'm reading for a networking exam, and I'm just wondering if I have missed something basic. Is there a need for more ip addresses than MAC addresses, and how would a node with one network adapter ...
12
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6answers
3k views

Best practice for dual-homing site with two ISPs?

I am subscribed to two ISPs, a fast expensive one and a cheap but slower one. They use different technologies, cable and ADSL, so there isn't much of a single point of failure, and all my comms ...
5
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3answers
594 views

address-family ipv6 on Cisco 3560G

Is anyone aware of an IOS version for the C3560G that supports configuring a neighbor to exchange IPv6 routes? Apparently 12.2(37)SE Advanced IP Services can't do it - as soon as you try to activate ...
12
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1answer
2k views

ASA5505 and IPv6 over a PPPoE Link

I see a lot of conflicting information about whether or not a Cisco ASA (5505 in this case) can use IPv6 over a PPPoE connection. I see official Cisco documentation making it look easy, but I see ...
13
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1answer
2k views

What is the maximum prefix size routed in the IPv6 Internet?

In v4, most of the operators filter BGP updates for prefixes longer than a /24, to preserve the size of the full view. What about IPv6 ? Is there such "convention" that stands out ?
15
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6answers
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Time to switch to IPv6?

I am thinking of upgrading our networking situation and am considering a migration of IPv4 to IPv6. Is it too soon to be considering this move as it looks like much of the networking gear and OSen ...
16
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5answers
2k views

How to choose a BGP router ID when using IPv6 only?

Usually, when using BGP, you can choose (or your device chooses four you) a router ID from one of your assigned public IP addresses. Now, let's admit you only run IPv6. As the router ID is still a 32 ...
12
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5answers
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What IPv6 prefixes should never be routed?

Seems clear to me that the Link Local, and Unique Local, addresses should at least be filtered. Is there anything other than LLA/ULA that should be filtered? For LLA, is it standard practice to ...
10
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3answers
3k views

Selecting IPv6 Unique Local Addresses (ie, choosing least-sig 40 bits)

We started with fec0::/10 for site-local addresses -- but that is now deprecated. Instead, we now have fc00::/7 reserved, with fd00::/8 dedicated to /48 nets for Unique Local Addresses. What's the ...
9
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3answers
288 views

Mitigating bad/malicious IPv6 RA announcements

In a Cisco environment (ISR-G2), how do I prevent, or mitigate, incorrect RA announcements? I see Cisco has "IPv6 RA Guard"... But does that just run on the router and "fight back" with correct RAs? ...
10
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4answers
1k views

Migration from IPv4 to IPv6 strategies

As everyone is aware we are out of IPv4 addresses and soon (if not already) we shall be moving on to IPv6. What are some good strategies and practices to migrate a complete IPv4 network onto IPv6?
9
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2answers
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Is TCP maximum segment size (MSS) “clamping” compatible with IPv6?

With IPv4, TCP MSS "clamping" (a network device editing the MSS value in a TCP header) can help when path maximum transmission unit discovery is not working. (e.g., when ICMP is being blocked ...
43
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4answers
45k views

Why is fe80::/10 reserved for link local addresses when fe80::/64 is actually used?

I understand that IPv6 reserves the fe80::/10 prefix for link local addresses, and that hosts select an address with a /64 prefix. Why is the reserved space so much larger than what is actually used ...
91
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12answers
28k views

IPv6 address space layout best practices

I'm comfortable with IPv4 address space allocations. By which I mean: Given services to plan for, or an organization to network, I have a good grasp of how to plan IP address space usage. (or at least,...

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