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38

One of the ideas around IPv6 was to speed up packet forwarding. To that end, several decisions were made. For example, the IPv6 header was greatly simplified and is a fixed length, unlike the variable length IPv4 header. Also, you cannot fragment IPv6 packets along the path, the way you can for IPv4, because packet fragmentation is resource intensive. Not ...


16

Because it's redundant. All the common link-layer protocols like Ethernet or WiFi have their own error checking and error correction mechanisms, so physical transmission errors are already unlikely. What's left are logic errors in the packet itself. But almost all transport protocols based on IPv6, like TCP or UDP, also have error checking to catch logical ...


14

It means that IP was designed for each endpoint only to maintain the state of the communications. NAT requires that the NAT device in the middle to maintain a state of the communications. IP was designed so that if something in the middle of that path changes, packets can be rerouted without any ill effect. If the path changes and misses the NAT device that ...


11

IP addresses are assigned to layer-3 interfaces (IP is a layer-3 protocol), either physical or virtual, and each interface can have multiple IP addresses. Multiple IP addresses are even required for IPv6, where you will have a Link-Local address and one or more Global and/or ULA addresses per interface. I will give you an IPv4 example that happens. DHCP is ...


11

What happens with a ping when it enters a network? Does the router redirects it to one of the devices on the network, or it sends the reply itself? A router routes packets towards the destination. An IP packet with ICMP payload (ICMP ping request) is treated no differently than any other packet. With "enter a network" you might be referring to routing a ...


7

Each interface requires an IP address of its own. Two different networks (subnets) require two different IP addresses, one from each network. You can bind multiple IP addresses to a single interface. When interfaces are bonded in some ways they can share an IP address (or address pool). A physical interface configured with multiple VLANs (on a trunk) ...


6

It's the host which is addressed in the outgoing ECHO REQUEST packet which is responsible for answering. As far as the routers in between are concerned, this is just like any other IP packet, and their job is just to get it to that host. Everything you need to know is in RFC 792 "Internet Control Message Protocol".


5

Ping is an application that sends ICMP Echo Requests to a destination and look for the destination to reply with an ICMP Echo Reply. ICMP is the payload of, although an integral part of, IP. That means that the ICMP Echo Request is encapsulated in an IP packet, and the IP packet has the destination IP address in the IP packet header. IP packets are sent to ...


5

End to end paradigm means that any host X with public IP a.b.c.d can directly connect to any host Y with public IP e.f.g.h (assuming IPv4 addressing, but the same thing applies to IPv6). The same must be true in both directions (X initiating connection to Y as well as Y initiating connection to X). This is how Internet used to work before we run out of IPv4 ...


4

HostA(10.10.10.100/24) -----.1/24 RTRA-56.0.0.1------WAN(INTERNET)-------12.0.0.100-RTRB Default gateway of HostA is inside interface of RTR-A Here is the ping packet flow, read slow and carefully, it might get confusing ping 12.0.0.100 from HOST-A at packet level sourceip will be hostA, src mac will be hosta dest ip will be 12.0.0.100 and mac will be ...


4

But in many cases, that public IP belongs to a whole network. For example a personal network. That is not correct. You are probably talking about Network address Translation (NAT), which is used on nearly all personal networks (and most commercial ones too). The IP address belongs to the NAT device (router or firewall). Networks do not have IP ...


3

Zac67 and Ron Maupin have briefly explained how multiple IP addresses per NIC work, which was probably the intent of the question. Here, I try to explain why one would add a second IP address to a host or gateway. In most cases nowadays, one would normally use multiple VLANs for these situations, with one subnet per VLAN. History VLANs were standardised ...


3

End to end means that host A on one side of the Internet can talk directly to host B on the other side of the internet. So e.g. I can ssh into a box in the US from Europe without any special configuration on any of the devices in between. When NAT is involved this is most likely not the case, e.g because some manual configuration is required on the NAT ...


2

Setting an IP address as a default gateway provides two things: allows the host to "find" (via ARP) the appropriate MAC address for L2 encapsulation informs the host which interface to use to find the gateway (via Routing table) Imagine a host has three network connections, each with unique IP address space. Typically, only one of those network connections ...


2

Packets are routed individually by destination IP address, regardless of any packets that have come before. A router does not maintain state (IP was specifically designed to be stateless), and routers route a packet based on the destination address, having no idea that it is in response to some other packet that went the other way. TCP, and other transport ...


1

In my case, the only thing you can ping in my network from the outside is the gw (which does port address translation) if it is IPv4. IPv6 ? When you can ping anything directly because in that case the route is thru a ipv6 tunnel. If the address you send the ping to is a connection on a router, that route will answer (maybe.)


1

In theory, you can connect to global IPv6 addresses from any other global IPv6 network in the world. In practice, we have firewalls that block outside-initiated traffic from entering a network unless there is an explicit rule allowing it. A firewall will, by default, block all outside-initiated traffic, and you must create rules to allow any such traffic to ...


1

For a point-to-multipoint interface (like an Ethernet NIC), the IP address of the next hop gateway is required - after all, the packet needs to finds its path through the network to that gateway. On a point-to-point interface (like a simple serial interface), no gateway address is required. Just routing out of the interface is sufficient since each ...


1

Segmentation and fragmentation, as the different names imply, serve different functions. Segmentation, which is a feature of transport protocols, serves to packetize a stream of data for reliable delivery. Fragmentation at the network level, ensures that the packet can be transmitted in a data link PDU. The transport layer can't depend on the lower layers ...


1

Server B connects to the origin server that is very close to server A and very far away from server B, since server A is closer, the response will be routed back to server A That's not the way it works. Anycast is used to shorten the route to global services: The same IP address is terminated in multiple locations and advertized over BGP. Now, clients ...


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