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Limitations of Broadband Speed Tweaks:
First, broadband tweaks should be made only after your network is tested and running reliably. Speed tweaks are performance optimizations only, not designed to fix installation errors or basic network configuration issues.
You should expect broadband tweaks might yield only small speed increases, and then only in certain situations. For example, a tweak to improve the performance of one online game may only benefit that title and then only initially when it is loading. Broadband tweaks may help certain applications like games but at the same time slow down others like Web browsing. In general, assume any performance benefits you obtain may be on the order of 10-20% gain rather than 100-200%.
Finally, speed tweaks also can create instability on some networks. Depending on the type of equipment and Internet service you use, some tweaks will be technically incompatible and need to be avoided.
Ref: http://compnetworking.about.com
IPv6 Addressing
IPv6 increases the size of the IP address from the 32 bits found in IPv4 to 128 bits. This increased size allows for a broader range of addressing hierarchies and a much larger number of addressable nodes.
In addition to the increased size, IPv6 addresses can be of different scopes that categorize what types of applications are suitable for the address. IPv6 does not support broadcast addresses, but uses multicast addresses to serve this role. In addition, IPv6 also defines a new type of address called anycast.
IPv6 addresses consist of eight hexadecimal groups. Each hexadecimal group, separated by a colon (:), consists of a 16-bit hexadecimal value. The following is an example of the IPv6 format:
xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx
A group of xxxx represents the 16-bit hexadecimal value. Each individual x represents a 4-bit hexadecimal value. The following is an example of a possible IPv6 address:
4FDE:0000:0000:0002:0022:F376:FF3B:AB3F
NOTE: Hexadecimal letters in IPv6 addresses are not case sensitive. |
IPv6 addresses often contain consecutive hexadecimal fields of zeros. To simplify address entry, you can use two colons (::) to represent the consecutive fields of zeros when typing the IPv6 address.Table 14 provides compressed IPv6 address format examples.
Table 14: Compressed IPv6 formats
IPv6 Address Type |
Full Format |
Compressed Format |
Unicast |
10FB:0:0:0:C:ABC:1F0C:44DA |
10FB::C:ABC:1F0C:44DA |
Multicast |
FD01:0:0:0:0:0:0:1F |
FD01::1F |
Loopback |
0:0:0:0:0:0:0:1 |
::1 |
Unspecified |
0:0:0:0:0:0:0:0 |
:: |
Table 15:
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NOTE: You can use two colons (::) only once in an IPv6 address to represent hexadecimal fields of consecutive zeros. |
An IPv6 address prefix is a combination of an IPv6 prefix (address) and a prefix length. The prefix takes the form ipv6-prefix/prefix-length and represents a block of address space (or a network). The ipv6-prefix variable follows general IPv6 addressing rules (see RFC 2373 for details). The /prefix-length variable is a decimal value that indicates the number of contiguous, higher-order bits of the address that make up the network portion of the address. For example, 10FA:6604:8136:6502::/64 is a possible IPv6 prefix.
IPv6 can use several types of addresses:
- Unicast - Used to identify a single interface, this release of the E-series router product supports the following unicast address types:
- Global aggregatable - Allows for aggregation of routing prefixes to limit the number of global routing table entries
- Link-local - Eliminates the need for a globally unique prefix. Local-link addresses allow communications between devices on a local link.
- Site-local - Used as private addresses to restrict communication to a domain portion.
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NOTE: IPv6 routers must not forward packets that have site-local source or destination addresses outside the site. |
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- IPv4-compatible - Contains a standard IPv4 address in the lower-order 32 bits of the address and zeros in the higher-order 96 bits of the address. For example, the format of an IPv4-compatible IPv6 address is 0:0:0:0:0:0:A.B.C.D (or condensed as ::A.B.C.D). In other words, devices using IPv6 use the entire 128-bit IPv4-compatible IPv6 address, whereas IPv4 devices use the IPv4 address embedded within the lower-order 32-bits of the address. You would use IPv4-compatible IPv6 addresses for devices that must support both IPv4 and IPv6 protocols.
- Multicast - Used for sending packets to multiple destinations. A multicast transmission sends packets to all interfaces that are part of a multicast group. The group is represented by the IPv6 destination address of the packet.
- Anycast - Used for a set of interfaces on different nodes. An anycast transmission sends packets to only one of the interfaces associated with the address, not to all of the interfaces. This interface is typically the closest interface, as defined by the routing protocol.
- Loopback - Used by a node to send an IPv6 packet to itself. An IPv6 loopback address functions the same as an IPv4 loopback address.
- Unspecified - Indicates the absence of an IPv6 address. For example, newly initialized IPv6 nodes may use the unspecified address as the source address in their packets until they receive an IPv6 address.
NOTE: IPv6 does not use broadcast addresses; instead, IPv6 uses multicast addresses. |
Some unicast and multicast IPv6 addresses contain a value known as scope. This value identifies the application suitable for the address.
Unicast addresses support two types of scope—global and local. In addition, there are two types of local scope—link-local addresses and site-local addresses.
Link-local unicast addresses, identified by the first ten bits of the prefix, function within a single network link. You cannot use link-local addresses outside a network link.
Site-local unicast addresses function within a site or an intranet. A site consists of multiple network links, and site-local addresses identify nodes inside the intranet. You cannot use site-local addresses outside the site.
Multicast addresses support 16 different types of scope, including node, link, site, organization, and global scope. A four-bit field in the prefix identifies the scope.
Unicast addresses identify a single interface. The address consists of n bits for the prefix and 128-n bits for the interface ID.
Multicast addresses identify a set of interfaces. The address is made up of the first 8 bits of all ones, a 4-bit flag field, a 4-bit scope field, and a 112-bit group ID.
11111111 | flgs | scop | group ID
The first octet of ones identifies the address as a multicast address. The flags field identifies whether the multicast address is a well-known address or whether it is a transient multicast address. The scope field identifies the scope of the multicast address. The 112-bit group ID identifies the multicast group.
Similar to multicast addresses, anycast addresses identify a set of interfaces. However, packets are sent to only one of the interfaces, not to all interfaces. Anycast addresses are allocated from the normal unicast address space and cannot be distinguished from a unicast address in format. Therefore, each member of an anycast group must be configured to recognize certain addresses as anycast addresses.
Internet Control Message Protocol (ICMP) provides a mechanism that enables a router or destination host to report an error in data traffic processing to the original source of the packet. For this release, the E-series router supports ICMP for use in the IPv6 ping and traceroute commands.
The ping and traceroute commands help you determine destination reachability within a network.
- Use the ping ipv6 command to send an ICMP echo request packet. In the following example, the request packet is sent to address 1::1 with a data size of 200 and a timeout value of 10 seconds:
host1#ping ipv6 1::1 data-size 200 timeout 10
- Use the traceroute ipv6 command to discover routes that router packets follow when traveling to their destination. In the following example, the trace destination address is 1::1, the maximum number of hops of the trace is 20, and the timeout value is 10 seconds:
host1#traceroute ipv6 1::1 hop-limit 20 timeout 10
Special Addresses in IPv6
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::/96 The zero prefix denotes addresses that are compatible with the previously used IPv4 protocol. |
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::/128 An IPv6 address with all zeroes in it is referred to as an unspecified address and is used for addressing purposes within a software. |
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::1/128 This is called the loop back address and is used to refer to the local host. An application sending a packet to this address will get the packet back after it is looped back by the IPv6 stack. The local host address in the IPv4 was 127.0.0.1. |
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2001:db8::/32 This is a documentation prefix allowed in the IPv6. All the examples of IPv6 addresses should ideally use this prefix to indicate that it is an example. |
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fec0::/10 This is a site-local prefix offered by IPv6. This address prefix signifies that the address is valid only within the local organization. Subsequently, the usage of this prefix has been discouraged by the RFC. |
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fc00::/7 This is called the Unique Local Address (ULA). These addresses are routed only within a set of cooperating sites. These were introduced in the IPv6 to replace the site-local addresses. These addresses also provide a 40-bit pseudorandom number that reduces the risk of address conflicts. |
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ff00::/8 This prefix is offered by IPv6 to denote the multicast addresses. Any address carrying this prefix is automatically understood to be a multicast address. |
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fe80::/10 This is a link-local prefix offered by IPv6. This address prefix signifies that the address is valid only in the local physical link. |
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