わくわくIT資格勉強記

• CE: Customer Edge Devices
• PE: Provider Edge Devices
• P: Provider Router

[CE Site A]-- PE -- P -- PE -- [CE Site B]

• SAP: Service Access Point
• SDP: Service Distribution Point
  • SDP ID はルータ内でuniqueであり、他ルータと共通のSDP IDとすることも可能
  • SDPは単一のサービスのためではなく、複数サービスで使用可能
• Service Tunnel encapsulation
  • MPLS/RSVP-TE
  • MPLS/LDP
  • IP/GRE
• Customer IDはプロバイダ内でuniqueであり、複数サービスで使用可能

Subscriber -- SAP -- Service/Customer -- SDP -- [Service Tunnel]

• LER: Label Edge Router as PE
• LSR: Label Switch Router as P

LER -- LSR -- LER

• ラベル配布のためのシグナリングプロトコル
  • LDP: Label Distribution Protocol
  • RSVP: Resource Reservation Protocol

• push(encapsulates the packet in a MPLS frame)
  • Ingress LSR
• pop(removes the packet from the MPLS frame)
  • Egress LSR
• swap(remove and add label)
  • LSR
• Label割り当ては片方向(unidirectional)のため、双方向通信のためにはもう片方からもLabel割り当てが必要。
• LDP neighborへのnext-hop解決にIGPが必要

• LSPと同様、片方向づつのLabel割り当及びIGPを必要とする
• 明示的なLSPのpath指定が可能
• Routing Protocolを利用してtraffic engineering(TE)が可能
• back-up LSPによるIGPよりも高速な切り替えが可能

Customer DataがCEからPEに届いたらinner Service Labelを付与し
outer transport labelを追加で付与しMPLS内に転送する。
宛先PEではすべてのLabelを取り除いて元のDataを宛先CEに送り出す。

• Point to Pointの専用線もしくは回線
  • Epipe: Ethernet
  • Apipe: ATM
  • Fpipe: Frame-Relay
  • Cpipe: TDM as a T1 or E1 circuit
• ProviderではMAC FDBのような管理はしない(一本の線だから)
• CustomerはEthernet VLAN tagや各種circuit IDを付与できる

• 基本的にVPWSと同じだがEthernet LAN Switchのように動作する
• PEはService IDごとにMAC FDBを持つ
  • CEのMAC addressがどのSAP or SDPの先にあるのか
• Unknown unicast frameがSAP or SDPに届いた場合、そのService IDのすべてのSAP, SDPにfloodingする

• IP Routerのように動作する
• PEはService IDごとに分離されたIP forwarding tableを持つ
• ProviderがCustomerにprivate IP addressを割り当てる
• 他のVPRN CustomerとIP address が overlappingしても問題ない
• VRF: VPN Routing and Forwarding Instances
• CEとPEが経路交換を行い、PE同士でも経路交換を行う
  • CEおよびPEではrouting protocolやstatic routeの設定が必要

　# configure router
　>config>router# bgp shutdown
　>config>router# no bgp
　protocolもinterfaceも動作していると削除できない。
　まずは shutdownしてから no で削除すること。
　# show router status
　BGPが動作していないことを確認

　# exec cf3:\OSPF-Full.cfg
　即座にConfigが反映される。旧Configを破棄して適用。

　# configure router ospf
　>config>router>ospf# area 0
　>config>router>ospf>area# no interface "toCE1"
　>config>router>ospf>area# exit all
　# show router ospf neighbor
　Interface-Nameから該当のIFが消えていればOK

　# configure router ldp
　>config>router>ldp$ interface-parameters
　>config>router>ldp>if-params$ interface "toPE2"
　>config>router>ldp>if-params>if>$ exit
　>config>router>ldp# no shutdown
　>config>router>ldp# exit
default disabledなのでno shutdownを忘れずに
対向のPEでも同様に設定

　>config>router>ldp# show router ldp interface
　>config>router>ldp# show router ldp session

SDP from PE1 to PE2 will be labeled 12
　*A:PE1# configure service
　*A:PE1>config>service>sdp$ sdp 12 mpls create
　*A:PE1>config>service>sdp$ far-end 150.10.0.1
　*A:PE1>config>service>sdp$ ldp
　*A:PE1>config>service>sdp$ no shutdown
sdp設定ではcreate parameterとmpls attributeを忘れずに
default disabledなのでno shutdownを忘れずに
対向のPEでも同様に設定
SDP from PE2 to PE1 will be labeled 21

　>config>service# show service sdp

削除する場合
　*A:PE1>config>service# sdp 12 shutdown
　*A:PE1>config>service# no sdp 12
片方向SDPの削除で対向SDPはUpしなくなる

　*A:PE1>config>service# sdp 12 shutdown

• Ethernetのdefault modeはnetworkである
• Customer向け（SAP）にはmode accessにする必要がある
• portをinterfaceに割り当てているとmodeを変更できない

　# configure router
　>config>router# interface "toCE1" shutdown
　>config>router# no interface "toCE1"
　>config>router# exit

　# configure port 1/1/1
　>config>port# shutdown
　>config>port# ethernet mode access
　>config>port# no shutdown
　>config>port# exit

（参考）

• MPLSを動作させるPortはnetworkにする必要がある
• ATMのdefault modeはaccess

1.IGP Verification

• show router ospf neighbor
• show router ospf interface

2.LDP Verification

• show router ldp bindings active
• show router ldp session
• show router ldp interface

3.SDP Verification

• show service sdp

4.SAP Verification

• show port 1/1/1

1.Create VPLS service
　# configure service
　>config>service# vpls 22 customer 1 create
　>config>service>vpls$ no shutdown
サービスIDはPE間およびProvider内でuniqueであること
ここではサービスIDを22としている。

2.Add the SDPs to the VPLS
　PE1>config>service>vpls$ mesh-sdp 12 create
　PE1>config>service>vpls>mesh-sdp$ exit
　PE1>config>service>vpls#

　PE2>config>service>vpls$ mesh-sdp 21 create
　PE2>config>service>vpls>mesh-sdp$ exit
　PE2>config>service>vpls#

3.Add the SAPs to attach CE devices to the VPLS.
　PE1>config>service>vpls# sap 1/1/1 create
　PE1>config>service>vpls>sap$ exit
　PE1>config>service>vpls#

　PE2>config>service>vpls# sap 1/1/1 create
　PE2>config>service>vpls>sap$ exit
　PE2>config>service>vpls#

• show service service-using

　Service IDとType（VPLS等）が確認可能

• show service id 22 base

　SAPに割り当てたPortやType(null:非802.1Q)
　SDP ID:Service IDが確認可能

• show service id 22 fdb detail

　CEのMACアドレスがどのSAP/SDPの先にあるか確認可能

---

Which of the following accurately describes a P device?
　A. It is used exclusively by the customer.
　B. It is responsible for adding and removing labels.
　C. It swaps label information and forwards packets.
　D. It creates an LSP in the provider network.

Answer A is a CE, and answer C is a P. D is partially correct, but B is the more accurate answer.

Which of the following is false regarding an SDP?
　A. It provides transport tunnel encapsulation.
　B. It is specific to a single service.
　C. The SDP ID is locally unique.
　D. LDP can be used as the signaling protocol.

SDPs are not specific to a single service and can support multiple services.

Which of the following is not an accurate description of a VPN?
　A. A series of point-to-point tunnels configured on client equipment
　B. A tunnel technology created in a provider network
　C. A function of MPLS networks to create private communities of users
　D. Any network that includes encryption

Encryption can be a part of a VPN, but the correct description of a VPN should include a way to privatize communications between user communities. The other answer speak to this, but answer D does not.

Which of the following is false regarding LDP?
　A. It is used to define unidirectional paths through the network.
　B. The LDP protocol is specifically intended for label distribution
　C. It is the only method for distributing labels in an MPLS network.
　D. It describes a path through the MPLS network based on the IGP.

LDP is only one method of distributing labels; RSVP can be used as well as other protocols.

Which of the following term-definition pairs is incorrect?
　A. push -- add a label
　B. swap -- replace a label
　C. label distribution protocol -- series of labels and next hop interface
　D. pop -- remove a label

This description is the Label Switched Path.

The most commonly used label distribution protocol is .
　A. OSPF
　B. BGP
　C. LDP
　D. RIP

LDP is the most common label distribution protocol.

Which of the following is not a type of VPN?
　A. VPWS
　B. VPNM
　C. VPLS
　D. VPRN

VPNM is not a type of VPN.

A VPN that provides a simple point-to-point service between two destinations is a .
　A. VPNM
　B. VPLS
　C. VPWS
　D. None of the above

VPWS is a VPN that emulates a point-to-point service between two destinations.

The VPN service that must maintain a table of MAC addresses is .
　A. VPWS
　B. VPLS
　C. VPRN
　D. Both A and B

VPLS is a VPN that must maintain a table of MAC addresses.

The VPN service that requires encryption is .
　A. VPNM
　B. VPLS
　C. VPWS
　D. None of the above

None of the VPN services provided by an MPLS network require encryption.

The VPN service that appears to the customer as a private routed network is .
　A. VPNM
　B. VPRN
　C. VPLS
　D. VPWS

VPRN is a VPN that appears to a customer as a private routed network.

As a packet traverses an MPLS network, it passes through a router that removes one label and replaces it with another.
The router it passed through was a router.
　A. PE
　B. CE
　C. LER
　D. P

P routers swap labels and forward them to other P or PE routers.

A packet arrives at a router with a label, and the router cannot perform any operations on it.
The router is most likely a .
　A. LSR
　B. PE
　C. LER
　D. None of the above

PE, LSR, and LER routers can all understand labels. The router is most likely a CE router, which is not one of the choices.

In an MPLS network, the customer routers have no knowledge of how the MPLS features are implemented.
The benefits of this include:
　A. Ease of CE configuration
　B. Allows for very scalable VPN solutions
　C. Lowers CE management overhead
　D. All of the above

Transparency of the MPLS features to a CE device has all of the benefits listed.

The relationship between LDP and an IGP is best described as
　A. LDP paths are preferred over IGP routes.
　B. LDP use IGP next-hop information.
　C. LDP re-distributes labels into IGP.
　D. IGP tags network destinations with LDP information.

LDP and IGPs do not re-distribute information directly or compete with each other for paths as they perform completely different functions, although LDP does use the information from IGP to populate the next-hop interfaces for labels.