最佳化Microsoft Office 365/Webex的AnyConnect拆分隧道

簡介

本文檔介紹如何使用設定配置ASA，以從VPN連線中排除發往Microsoft Office 365(Microsoft Teams)和Cisco Webex的流量。

背景資訊

配置自適應安全裝置(ASA)還為支援自適應安全裝置的AnyConnect客戶端引入網路地址排除和基於動態完全限定域名(FQDN)的排除。

分割通道

需要將ASA配置為從隧道中排除指定的IPv4和IPv6目標清單。遺憾的是，地址清單是動態的，並且可能會更改。有關python指令碼和聯機python讀取/評估列印循環(REPL)的連結，請參閱「配置」一節，此循環可用來檢索清單和生成示例配置。

動態分割通道

除了分割排除網路地址清單之外，在Windows和Mac版AnyConnect 4.6中還新增了動態分割隧道。動態分割隧道使用FQDN來確定連線是否可以經過隧道。Python指令碼還確定要新增到自定義AnyConnect屬性的終結點的FQDN。

組態

在Python 3 REPL中運行此指令碼，或在公共REPL環境(如AnyConnectO365DynamicExclude)中運行此指令碼

import urllib.request
import uuid
import json
import re


def print_acl_lines(acl_name, ips, section_comment):
    slash_to_mask = (
        "0.0.0.0",
        "192.0.2.1",
        "192.0.2.1",
        "10.224.0.0",
        "10.240.0.0",
        "10.248.0.0",
        "10.252.0.0",
        "10.254.0.0",
        "10.255.0.0",
        "10.255.128.0",
        "10.255.192.0",
        "10.255.224.0",
        "10.255.240.0",
        "10.255.248.0",
        "10.255.252.0",
        "10.255.254.0",
        "10.255.255.0",
        "10.255.255.128",
        "10.255.255.192",
        "10.255.255.224",
        "10.255.255.240",
        "10.255.255.248",
        "10.255.255.252",
        "10.255.255.254",
        "10.255.255.255",
        "10.255.255.255",
        "10.255.255.255",
        "10.255.255.255",
        "10.255.255.240",
        "10.255.255.248",
        "10.255.255.252",
        "10.255.255.254",
        "10.255.255.255",
    )
    print(
        "access-list {acl_name} remark {comment}".format(
            acl_name=acl_name, comment=section_comment
        )
    )
    for ip in sorted(ips):
        if ":" in ip:
            # IPv6 address
            print(
                "access-list {acl_name} extended permit ip {ip} any6".format(
                    acl_name=acl_name, ip=ip
                )
            )
        else:
            # IPv4 address.  Convert to a mask
            addr, slash = ip.split("/")
            slash_mask = slash_to_mask[int(slash)]
            print(
                "access-list {acl_name} extended permit ip {addr} {mask} any4".format(
                    acl_name=acl_name, addr=addr, mask=slash_mask
                )
            )


# Fetch the current endpoints for O365
http_res = urllib.request.urlopen(
    url="https://endpoints.office.com/endpoints/worldwide?clientrequestid={}".format(
        uuid.uuid4()
    )
)
res = json.loads(http_res.read())
o365_ips = set()
o365_fqdns = set()
for service in res:
    if service["category"] == "Optimize":
        for ip in service.get("ips", []):
            o365_ips.add(ip)
        for fqdn in service.get("urls", []):
            o365_fqdns.add(fqdn)

# Generate an acl for split excluding For instance
print("##### Step 1: Create an access-list to include the split-exclude networks\n")
acl_name = "ExcludeSass"
# O365 networks
print_acl_lines(
    acl_name=acl_name,
    ips=o365_ips,
    section_comment="v4 and v6 networks for Microsoft Office 365",
)
# Microsoft Teams
# https://docs.microsoft.com/en-us/office365/enterprise/office-365-vpn-implement-split-tunnel#configuring-and-securing-teams-media-traffic
print_acl_lines(
  acl_name=acl_name,
  ips=["10.107.60.1/32"],
  section_comment="v4 address for Microsoft Teams"
)
# Cisco Webex - Per https://help.webex.com/en-us/WBX000028782/Network-Requirements-for-Webex-Teams-Services
webex_ips = [
    "10.68.96.1/19",
    "10.114.160.1/20",
    "10.163.32.1/19",
    "192.0.2.1/18",
    "192.0.2.2/19",
    "198.51.100.1/20",
    "203.0.113.1/19",
    "203.0.113.254/19",
    "203.0.113.2/19",
    "172.29.192.1/19",
    "203.0.113.1/20",
    "10.26.176.1/20",
    "10.109.192.1/18",
    "10.26.160.1/19",
]
print_acl_lines(
    acl_name=acl_name,
    ips=webex_ips,
    section_comment="IPv4 and IPv6 destinations for Cisco Webex",
)

# Edited. April 1st 2020
# Per advice from Microsoft they do NOT advise using dynamic split tunneling for their properties related to Office 365
#
print(
    "\n\n##### Step 2: Create an Anyconnect custom attribute for dynamic split excludes\n"
)
print("SKIP.  Per Microsoft as of April 2020 they advise not to dynamically split fqdn related to Office365")
#print(
#    """
#webvpn
#  anyconnect-custom-attr dynamic-split-exclude-domains description dynamic-split-exclude-domains
#
#anyconnect-custom-data dynamic-split-exclude-domains saas {}
#""".format(
#        ",".join([re.sub(r"^\*\.", "", f) for f in o365_fqdns])
#    )
#)
#
print("\n##### Step 3: Configure the split exclude in the group-policy\n")
print(
    """
group-policy GP1 attributes
 split-tunnel-policy excludespecified
 ipv6-split-tunnel-policy excludespecified
 split-tunnel-network-list value {acl_name}
""".format(
        acl_name=acl_name
    )
)

注意:Microsoft建議使用發佈的IPv4和IPv6地址範圍配置分割隧道，將發往關鍵Office 365服務的流量從VPN連線範圍中排除。為了獲得最佳效能並最有效地使用VPN容量，可以直接在VPN隧道之外路由與Office 365 Exchange Online、SharePoint Online和Microsoft Teams（在Microsoft文檔中稱為「最佳化」類別）關聯的這些專用IP地址範圍的流量。有關此建議的更多詳細資訊，請參閱使用VPN拆分隧道最佳化遠端使用者的Office 365連線。

註：截至2020年4月初，Microsoft Teams有一個依賴關係，即必須從隧道中排除IP範圍10.107.60.1/32。有關詳細資訊，請參閱配置和保護Teams媒體流量。

驗證

連線使用者後，您會看到用ACL中提供的地址填充的非安全路由以及動態隧道排除清單。