M PLS :
What is MPLS (Multi-protocol label switching ) : MPLS is a packet-forwarding technology which uses labels to make data forwarding decisions. With MPLS, the Layer 3 header analysis is done just once when the packet enters the MPLS domain. MPLS impose a label in a packet between data link layer and network layer . label 0-15 are reserved label.
LSR : label switching router /provider router which called as P router
edge LSR / provider edge (PE) router : which is called as PE router
Label distribution protocol (LDP)
TDP : tag distribution protocol by Cisco uses TCP /UDP port 711 uses 224.0.0.2 all router in multicast subnet
LDP : uses TCP/UDP port 646 and 224.0.0.2
Forwarding information base (FIb) which CEF table : “show ip cef” will show you details
label information Base (LiB) “show MPLS ldp binding” command will show details of LIB.
label forwarding information base (LFIB ) which is action table, “ show MPLS forwarding-table” command will show forward table .
MPLS default hello interval is 5 sec and hold time is 15 second
MPLS control plane :
where L3 routing protocol exist
where label exchange protocol exist LDP/TDP
control plane take care of exchanging routing information conjunct with LDP.
LDP assigns a label to a route for its incoming and outgoing interface, for
instance network 10.0.0.0/8 gets a label 24 for incoming interface and 25 for outgoing
interface
only PE router looks routing lookup and does label removal .
MPLS Data plane /forwarding plane:
sends data based on L3 or L2 information
takes care of label swapping in other word data plane take cares of LFIB
MPLS process :
1.router build routing table by routing protocol
2. the mpls-enabled routers assign label to each route
3. the routers advertise the route to other LSRs
4. all LSRs build their FIBs, LIBs and LFIBs table
Some Important command :
shw mpls ldp discovery details
show mpls ldp parameters
show mpls forwarding table
show mpls ldp binding
show mpls ip binding
PHP = penultimate hop popping does not work in ATM ( a label gets remove by the P router before it sending to PE router , to reducing table lookup in PE router)
VRF = virtual routing and forwarding
MPLS VPN terms :
Route Distinguisher : (RD) keep customer routes unique with a number
Route Target (RT) : route target number can be use for import and export routes , has to be identical on PE router
.
PE /Edge LSR router keeps following information :
control plane : routing protocol
ip routing table
label distribution protocol
Data plane : ip forwarding table
label forwarding table
in ATM VPI and VCI is used as label , and its called cell mode MPLS
MPLS traffic engineering require OSPF or is-is routing protocol
LSP = label switch path , LSP build by routing protocol
in MPLs VPN route summarization should not be use , because in vpn end to end LSPs are required
the LSR assigns a label to a network connected locally and advertise the to all neighbor , saying this is the label for my network .
MPLS is defend on IGP protocol for loop prevention although it has 8 bit TTL value , when time to leave value decrease to 0 the packet gets drop , to prevent endless loop. TTL value by default on in Cisco router.
but can be disable , the benefit is if some one does trace route it will show core LSR in trace if TTL blocked in LSR. if TTL disable , should have to disable in all Router .
MPLS frame mode uses per platform labels , this is not secure , and causes label spoofing attack , can call it unsolicited downstream label distribution
MPLS ATM mode uses per interface labels , ATM use downstream on demand approach
router with higher ip address initiate TCP session , loopback beats physical interface , higher is batter
uni-cast IP address also can be used to form neighbor , instead 224.0.0.2 .
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