3.0 IP Connectivity 3.3 Configure and verify IPv4 and IPv6 static routing 3.3.a Default route 3.3.b Network route 3.3.c Host route 3.3.d Floating static

1. Chapter - 25
Implementing
IPv6 RoutingCCNA
200-301
BY : Vishnu3.0 IP Connectivity
3.3 Configure and verify IPv4 and IPv6 static routing
3.3.a Default route
3.3.b Network route
3.3.c Host route
3.3.d Floating static

2. Connected and Local IPv6 Routes
• A router adds IPv6 routes in its routing table based of below conditions.
Connected and Local routes.
Statically configured routes.
Via a routing protocol like OSPFv3.
Lets discuss one by one ….
Rules for Connected and Local Routes
• Routers add and remove connected routes and local routes, based on the interface configuration and the
interface state.
• Connected and Local route follows same logic as Connected represents subnet and Local represents
specific IPv6 address.
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3. Example of Connected IPv6 Routes
You can also use show ipv6 route connected or show ipv6 route local
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4. Static IPv6 Routes
• Static routes require direct configuration with the ipv6 route command.
• The ipv6 route command follows the same general logic as does IPv4’s ip route command.
2. Using Global
address
1.Using Exit interface
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5. Example Static Route with a Link-Local Next-Hop Address
Unlike other two here you have to give the next hop link local IP and exit interface. As the IP is local
to link
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6. Floating Static IPv6 Routes
• What if the static route want to compete with other static route or with dynamic routing protocol.
• The best path selection is purely based on AD –Administrative Distance value. Lowest wins.
• For static route its 1 and OSPF its 110
• In the above network T1 link will be used which is not intended by any engineer because of low speed.
• Hence we can manipulate the AD value of static higher than OSPF.
ipv6 route 2001:db8:1111:7::/64 2001:db8:1111:9::3 130
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8. Troubleshooting Static IPv6 Routes – Last Section
• You cannot use own interface IPv6 address as next hop address
I cannot use 2001:DB8:9:2::1/ on R1 to reach B
■ For ipv6 route commands that list an outgoing interface, that interface must be in an
up/up state.
■ For ipv6 route commands that list a global unicast or unique local next-hop IP address
(that is, not a link-local address), the local router must have a route to reach that next-hop
address.
■ If another IPv6 route exists for that exact same prefix/prefix-length, the static route must
have a better (lower) administrative distance.
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9. The Neighbor Discovery Protocol
• Similar to ICMP for IPv4, IPv6 defines the ICMP protocol for IPv6 (ICMPv6).
• For IPv4 the ARP works as separate protocol. For IPv6 we have NDP Neighbor Discovery Protocol.
• NDP protocol (RFC 4861)- https://tools.ietf.org/html/rfc4861
Neighbor MAC Discovery: An IPv6 LAN-based host will need to learn the MAC address
of other hosts in the same subnet. NDP replaces IPv4’s ARP, providing messages that
replace the ARP Request and Reply messages.
Router Discovery: Hosts learn the IPv6 addresses of the available IPv6 routers in the same
subnet.
SLAAC: When using Stateless Address Auto Configuration (SLAAC), the host uses NDP
messages to learn the subnet (prefix) used on the link plus the prefix length.
DAD: Before using an IPv6 address, hosts use NDP to perform a Duplicate Address
Detection (DAD) process, to ensure no other host uses the same IPv6 address before
attempting to use it.
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10. 1. Discovering Neighbor Link Addresses with NDP NS and NA
• NDP replaces IPv4 ARP using a pair of matched solicitation and advertisement messages: the Neighbor
Solicitation (NS) and Neighbor Advertisement (NA) messages.
• Basically NS acts as ARP request and ND acts as ARP reply.
Neighbor Solicitation (NS): This message asks the host with a particular IPv6 address (the
target address) to reply with an NA message that lists its MAC address.
Neighbor Advertisement (NA): This message lists the sender’s IPv6 and MAC addresses.
It can be sent in reply to an NS message, and if so, the packet is sent to the IPv6 unicast
address of the host that sent the original NS message.
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11. Discovering Routers with NDP RS and RA
• IPv4 hosts use the concept of an IPv4 default gateway or default router.
• When the router needs to send a packet to different network it used default gateway IP.
• In an IPv4 network we can manually configure default gateway or we can get using DHCP.
• However, The IPv6 uses NDP to learn the default gateway.
NDP defines two messages (RS and RA)
Router Solicitation (RS): This message is sent to the “all-IPv6-routers” local-scope multicast
address of FF02::2 so that the message asks all routers, on the local link only, to identify
themselves.
Router Advertisement (RA): This message, sent by the router, lists many facts, including
the link-local IPv6 address of the router. When sent in response to an RS message, it flows
back to either the unicast address of the host that sent the RS or to the all-IPv6-hosts
address FF02::1.

12. Using SLAAC with NDP RS and RA
• Both IPv4 and IPv6 support the idea of dynamic address assignment for hosts via the Dynamic Host
Configuration Protocol (DHCP).
• A PC will send a message to DHCP server asking IP, DHCP check if any duplicate IP is their in the link once it
finds out it leases the IP.
• In IPv6 we don’t need the intervention of DHCP to get an IP -Stateless Address Autoconfiguration (SLAAC).
1. Learn the IPv6 prefix used on the link, from any router, using NDP RS/RA messages.
2. Build an address from the prefix plus an interface ID, chosen either by using EUI-64
rules or as a random value.
3. Before using the address, first use DAD to make sure that no other host is already
using the same address.
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13. Discovering Duplicate Addresses Using NDP NS and NA
• No matter whether using SLAAC, DHCP, or static address configuration hosts uses DAD before assigning an
IP to itself. ? In DHCP if both PC and DHCP server uses DAD, answer is Yes.
• The term DAD refers to the function, but the function uses NDP NS and NA messages.
• Basically, a host sends an NS message for its own IPv6 address and sees if anybody replying.
• No other host should be using that address, so no other host should send an NDP NA in reply
1. PC1, before using address 2001:DB8:1111:1::11, must use DAD.
2. PC1 sends an NS message, listing the address PC1 now wants to use
(2001:DB8:1111:1::11) as the target.
3. PC2 receives the NS, sees what PC2 already uses as its own address, and sends back
an NA.
4. PC1, on receiving the NA message for its own IPv6 address, realizes a duplicate
address exists.
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